Gasoline

Liquid Fuel Derived from Petroleum

For those still navigating the labyrinth of nomenclature, “Petrol” will lead you to Petrol (disambiguation) , and “Gasoline” to Gasoline (disambiguation) . One might wonder why such clarity is required for something so ubiquitous, but here we are.

Gasoline (North American English ), or as it’s known to those across the pond, petrol (Commonwealth English ), is, at its core, a petrochemical product. It presents itself as a transparent, often faintly yellowish, and undeniably flammable liquid . Its primary, indeed almost singular, purpose in the grand scheme of human endeavor is to serve as a fuel for those rather energetic spark-ignited internal combustion engines that propel a significant portion of our mobile existence. When meticulously formulated for these engines , gasoline reveals itself as a complex chemical tapestry, woven from organic compounds painstakingly teased out from the raw, unrefined depths of petroleum through a process known as fractional distillation . Following this initial separation, it is then further refined and chemically augmented with a variety of gasoline additives , each designed to coax out specific performance characteristics. This intricate dance of chemistry and engineering culminates in a product that is not just essential, but also a consistently high-volume, remarkably profitable commodity within the sprawling ecosystem of crude oil refineries. [1]

The intrinsic capacity of any given gasoline blend to resist the rather inconvenient phenomenon of premature ignition—a self-destructive tendency that manifests as audible knocking and, quite predictably, diminishes the operational efficiency of reciprocating engines —is quantified by its octane rating . Historically, and with a rather cavalier disregard for future consequences, tetraethyl lead was extensively employed to artificially elevate this octane rating. However, in a rare moment of collective foresight, it has been largely expunged from modern automotive gasoline formulations, primarily due to the well-documented and rather severe health hazard posed by lead compounds. Curiously, or perhaps inevitably, certain specialized applications such as aviation , various off-road motor vehicles, and the inherently competitive realm of racing car engines continue to utilize leaded gasolines, seemingly clinging to the past with a tenacity matched only by the pursuit of speed. [2] [3] Beyond the question of knocking, numerous other substances are routinely introduced into gasoline. These additions serve a spectrum of purposes: enhancing chemical stability, optimizing overall performance, mitigating corrosion within fuel systems, and even providing a degree of self-cleaning for the fuel delivery infrastructure. Furthermore, gasoline mixtures frequently incorporate oxygen-containing chemicals, such as ethanol , MTBE , or ETBE , ostensibly to foster more complete and efficient combustion . One might observe that humanity is quite adept at creating problems and then devising elaborate, often temporary, solutions for them.

History and etymology

The very origins of the terms we use for this ubiquitous liquid are, like most things, rooted in history. One could almost hear the cosmic sigh as linguists meticulously traced the lineage. English dictionaries, in their infinite wisdom, reveal that the term “gasoline” is a compound, ingeniously derived from “gas”—a rather broad and unspecific term, wouldn’t you agree?—appended with the chemical suffixes “-ole” and “-ine.” [4] [5] [6] Meanwhile, the term “petrol” takes a slightly more direct, if equally uninspired, route, stemming from the Medieval Latin word petroleum. This, in turn, is a straightforward composite of petra, meaning “rock,” and oleum, meaning “oil.” One can almost picture the ancient Roman, pointing at a viscous seep and declaring, “Ah, rock oil. How terribly imaginative.” [7]

The real impetus for the focused development of gasoline-like fuels began, rather predictably, with humanity’s incessant drive to move faster and more efficiently. This interest ignited with the invention of internal combustion engines that proved sufficiently robust and practical for widespread adoption in transportation applications. These groundbreaking machines, famously known as Otto engines after their principal developer, were meticulously engineered and refined in Germany during the final quarter of the 19th century. The initial fuel source for these pioneering engines was a relatively volatile hydrocarbon compound, conveniently extracted from coal gas . With a boiling point hovering around 85 °C (185 °F)—a temperature considerably lower than, say, n-octane, which boils at a more robust 125.62 °C (258.12 °F) [8] —this early fuel was remarkably well-suited for the rudimentary carburettors (essentially evaporators) of the era. The subsequent invention and widespread adoption of the “spray nozzle” carburettor marked a significant leap forward, liberating engine designers from the constraints of highly volatile fuels and enabling the use of less temperamental, and often more abundant, liquid fuels.

As engineers relentlessly pursued greater efficiency, attempts were made to operate these engines at increasingly higher compression ratios . However, these early endeavors were consistently thwarted by a persistent and destructive issue: the premature, uncontrolled explosion of the fuel-air mixture within the cylinder, a phenomenon universally recognized as knocking . This mechanical impediment served as a stark reminder that simply cramming more air and fuel together wasn’t always the optimal path. A critical breakthrough in the production of suitable fuels arrived in 1891 with the advent of the Shukhov cracking process . This innovative method became the world’s first commercially viable technique for breaking down the heavier, less useful hydrocarbons found in crude oil. By cleaving these larger molecules into smaller, lighter ones, the Shukhov process dramatically increased the yield of more desirable, volatile products compared to the simpler, less efficient method of straight distillation. It was an early, crucial step in bending crude oil to humanity’s burgeoning will.

Chemical analysis and production

One might assume that something so commonplace as gasoline is a simple, straightforward substance. One would, of course, be incorrect. Commercial gasoline, much like other liquid fuels used for transportation, is a singularly complex medley of hydrocarbons . [9] Its performance specifications are not static; they are, in fact, rather temperamental, varying even with the seasons. Less volatile blends are explicitly mandated during the warmer months, a pragmatic measure designed to minimize evaporative losses, which, if left unchecked, contribute rather inconveniently to atmospheric pollution.

Gasoline is not born but made in specialized industrial complexes known as oil refineries . From a single 160-liter (42 U.S. gal) barrel of crude oil , approximately 72 liters (19 U.S. gal) of gasoline can be extracted. [10] The initial material isolated directly from crude oil through the primary distillation process, often referred to as virgin or straight-run gasoline, is, rather disappointingly, inadequate for the demands of modern engines. Its octane rating , in particular, falls far short of contemporary specifications. Nevertheless, this raw fraction serves a purpose, being pooled into the broader gasoline blend, acting as a foundational component that will later be transformed and enhanced.

The lion’s share of a typical gasoline formulation consists of a homogeneous, though intricately varied, mixture of hydrocarbons . These molecules generally possess between four and twelve carbon atoms (a range commonly, and rather succinctly, denoted as C4–C12). [11] It is not a single compound but a diverse cocktail comprising paraffins (more correctly termed alkanes ), olefins (alkenes ), naphthenes (cycloalkanes ), and aromatics . The oil industry, ever fond of its own specialized lexicon, insists on using “paraffin” in place of the standard chemical nomenclature “alkane,” a minor but persistent quirk. The precise chemical makeup of any given gasoline is not arbitrary; it is a direct consequence of several key factors:

• The specific oil refinery responsible for its production, as not all refineries are equipped with the identical array of advanced processing units.
• The particular batch of crude oil feedstock fed into that refinery, given that crude oil itself is a variable commodity.
• The desired grade of gasoline being manufactured, with the octane rating being a paramount determinant.

The various streams that emerge from a refinery and are subsequently blended to create the final gasoline product each possess distinct characteristics. Some of the most significant of these streams include:

• Straight-run gasoline, sometimes known more broadly as naphtha (and further subdivided into light straight-run naphtha “LSR” and light virgin naphtha “LVN”), is the direct distillate from crude oil. Once the primary source of fuel, its inherently low octane rating necessitated the widespread use of organometallic fuel additives, most notably tetraethyllead , a practice that thankfully began its phaseout in the United States in 1975. [12] Straight-run naphtha typically exhibits a low aromatic content (though this can fluctuate based on the specific crude oil stream), contains some cycloalkanes (naphthenes), and, crucially, is entirely devoid of olefins (alkenes ). Only a fraction, typically between 0 and 20 percent, of this stream is incorporated into the final gasoline blend. This limitation arises because the quantity of this fraction found in crude oil is generally insufficient to meet fuel demand, and its Research Octane Number (RON) is simply too low for modern requirements. The chemical properties of straight-run gasoline, particularly its RON and Reid vapor pressure (RVP), can be significantly improved through processes like reforming and isomerization . However, prior to being fed into these more advanced units, the naphtha must first be meticulously separated into its light and heavy components. Intriguingly, straight-run gasoline can also be diverted from fuel production to serve as a vital feedstock for steam crackers , which produce valuable olefins for the petrochemical industry.

• Reformate, a product meticulously crafted from straight-run gasoline within a catalytic reformer , boasts a commendably high octane rating . This is primarily due to its elevated aromatic content, while simultaneously maintaining a relatively low olefin content. It’s worth noting that many of its constituent compounds, such as benzene , toluene , and xylene —collectively referred to as BTX hydrocarbons—are often more valuable as chemical feedstocks for other industries and are thus, to varying degrees, extracted. Furthermore, the BTX content in gasoline is subject to stringent regulatory limits, adding another layer of complexity to its formulation.

• Catalytic cracked gasoline, also frequently referred to as catalytic cracked naphtha , is the output of a catalytic cracker . This stream possesses a moderate octane rating , a notably high olefin content, and a moderate aromatic content, making it a distinct contributor to the overall blend.

• Hydrocrackate, which comes in heavy, mid, and light fractions, is generated through the operation of a hydrocracker . It typically features a medium to low octane rating and moderate levels of aromatics .

• Alkylate is meticulously produced in an alkylation unit, utilizing isobutane and C3-/C4-olefins as its primary feedstocks. The finished alkylate is remarkable for containing absolutely no aromatics or olefins and possesses a high MON (Motor Octane Number ). This particular blend proved its worth during World War II, serving as a critical component in aviation fuel . [13] More recently, since the late 1980s, it has found a niche market as a specialty fuel, particularly for handheld gardening and forestry tools equipped with internal combustion engines, a testament to its clean-burning properties. [14] [15]

• Isomerate is obtained through the process of isomerizing low-octane straight-run gasoline, transforming it into iso-paraffins—which are, for the uninitiated, non-chain alkanes , such as the well-known isooctane . Isomerate delivers a respectable medium RON and MON, and, like alkylate, is free of aromatics or olefins.

• Butane is a common, though carefully controlled, component blended into the gasoline pool. The quantity of this stream is, however, strictly limited by the RVP (Reid Vapor Pressure) specification, as its volatility needs to be managed for safe and efficient engine operation.

• Oxygenates, more precisely defined as alcohols and esters , are frequently blended into the fuel pool, particularly in the U.S. where ethanol is the dominant choice. In Europe and other nations, blends may contain ethanol alongside Methyl tertiary-butyl ether (MTBE) and Ethyl tert-butyl ether (ETBE). MTBE, once a prevalent additive in the United States, faced a significant backlash and was largely banned by most states in the early to mid-2000s due to environmental concerns. [16] A few countries, notably China, still permit the direct blending of methanol into gasoline, [17] though this practice is less common elsewhere. The subject of oxygenates and their blending receives further, more detailed attention later in this article, for those who find such complexities compelling.

It is perhaps redundant to state, but these terms are the specialized vernacular, the peculiar jargon, employed within the oil industry. And, as is often the case with such specialized language, the precise terminology can and does vary depending on region and specific corporate practice.

In a commendable, if somewhat belated, effort to mitigate environmental impact, many countries have now imposed strict limits on the overall aromatics content in gasoline, with particularly tight restrictions on benzene , and also on olefin (alkene ) content. Such regulations have, quite logically, spurred a growing preference for alkane isomers, such as isomerate or alkylate, in gasoline formulations, primarily because their octane rating is inherently superior to that of normal n-alkanes. Within the European Union , the benzene limit is rigorously set at one percent by volume for all grades of automotive gasoline. This stringent target is typically achieved by carefully avoiding the feeding of C6 hydrocarbons, especially cyclohexane , into the reformer unit, where it would, quite predictably, be converted into benzene. Thus, only (desulfurized) heavy virgin naphtha (HVN) is typically processed in the reformer unit, a precise dance of chemistry and regulation. [18]

Beyond these primary components, gasoline can also contain other organic compounds , such as various organic ethers (added deliberately for specific purposes), along with trace levels of contaminants. Among these, organosulfur compounds are particularly notable, though they are usually meticulously removed at the refinery to prevent adverse effects on engine performance and emissions.

On average, a U.S. petroleum refinery, from each 160-liter (42 U.S. gallons) barrel of crude oil , typically produces approximately 72 to 76 liters (19 to 20 U.S. gallons) of gasoline, alongside 41 to 49 liters (11 to 13 U.S. gallons) of distillate fuel (diesel fuel ), and an additional 11 to 15 liters (3 to 4 U.S. gallons) of jet fuel . It is important to acknowledge that this product ratio is not fixed; it is a dynamic outcome, contingent upon the specific processing capabilities available within an oil refinery and, of course, the inherent quality and composition revealed by the crude oil assay . [19]

Physical properties

It’s a marvel of human ingenuity, this stuff. Or perhaps just a testament to our stubbornness.

Density

The specific gravity of gasoline typically spans a range from 0.71 to 0.77. [20] It’s a rather straightforward correlation: higher densities within this range generally indicate a greater volume fraction of aromatics within the blend. [21] In the European market, finished, commercially viable gasoline is commonly traded using a standard reference density of 0.755 kilograms per liter (equivalent to 6.30 lb/U.S. gal, or 7.5668 lb/imp gal). The price of a given shipment is then adjusted—either escalated or de-escalated—based on its actual measured density, a rather precise way to account for variations in composition. [clarification needed] This low density has a rather important, if obvious, consequence: gasoline floats on water. Consequently, water, when applied in anything less than a meticulously fine mist, is generally ineffective in extinguishing a gasoline fire. One might even say it exacerbates the problem, spreading the inferno rather than quelling it.

Stability

This section, apparently, requires further validation. One might suggest that if the information isn’t already obvious, perhaps the problem lies elsewhere. Nevertheless, for the sake of thoroughness, let us proceed.

Quality gasoline, when stored under optimal conditions, should retain its essential characteristics and remain stable for a period of approximately six months. Beyond this initial window, however, a gradual degradation process is to be expected. [22] Even gasoline that has been stored for a full year will, in most instances, still be capable of combustion within an internal combustion engine without encountering insurmountable difficulties. [22] The ideal storage scenario dictates an airtight container, specifically designed to thwart oxidation and prevent the ingress of water vapor, which can wreak havoc on fuel integrity. Furthermore, this container must be robust enough to withstand the inherent vapor pressure of the gasoline without resorting to venting, a crucial measure to prevent the undesirable loss of the more volatile fractions of the fuel. Maintaining a stable, cool temperature is also paramount, as it serves to mitigate excessive pressure buildup from liquid expansion and, perhaps more critically, to decelerate the rate of any unwelcome decomposition reactions. When gasoline is neglected and not stored in accordance with these best practices, the inevitable consequence is the formation of gums and solids. These undesirable byproducts can lead to corrosion of vital system components and accumulate on wet surfaces, a condition colloquially, and rather aptly, termed “stale fuel.” Gasoline that contains ethanol is particularly susceptible to this process, possessing an unfortunate propensity to absorb atmospheric moisture. This absorption then often leads to the formation of gums, solids, or, in a more problematic scenario, the separation into two distinct phases: a hydrocarbon phase languidly floating atop a less useful water-alcohol phase. [22]

The insidious presence of these degradation products, whether lurking within the fuel tank, the fuel lines, or the intricate components of a carburettor or fuel injection system, inevitably complicates the engine starting process or, at the very least, results in a noticeable reduction in engine performance. [23] Upon the resumption of regular engine use, this accumulated buildup may or may not be effectively purged by the continuous flow of fresh gasoline; it’s a gamble, really. The judicious addition of a fuel stabilizer to gasoline can, to a certain extent, prolong the useful life of fuel that cannot, for whatever reason, be stored under ideal conditions. However, it bears repeating that the only truly definitive solution for the long-term storage of an engine, machine, or vehicle is the complete and thorough removal of all fuel from its system. Typical fuel stabilizers are proprietary concoctions, often comprising mineral spirits , isopropyl alcohol , 1,2,4-trimethylbenzene , or various other additives . These stabilizers are particularly popular, and indeed highly recommended, for small engines, such as those found in lawnmowers and tractors, especially when their usage is sporadic or seasonal, characterized by prolonged periods of inactivity. Users are commonly advised to ensure gasoline containers remain more than half full and are properly sealed to minimize exposure to air, to scrupulously avoid storage at elevated temperatures, to operate an engine for approximately ten minutes to ensure the stabilizer circulates through all components prior to storage, and, for good measure, to periodically run the engine to purge any lingering stale fuel from the carburettor. [11] One wonders if such vigilance is truly worth the effort for a lawnmower.

The stringent requirements governing gasoline stability are meticulously outlined by the standard ASTM D4814. This comprehensive standard delineates the various characteristics and necessary requirements for automotive fuels, ensuring their suitability for use across a broad spectrum of operating conditions in ground vehicles equipped with spark-ignition engines.

Combustion energy content

A gasoline-fueled internal combustion engine , in its fundamental operation, extracts useful energy from the vigorous combustion of gasoline’s myriad hydrocarbons with oxygen , obligingly drawn from the ambient air. This rather energetic chemical reaction yields, as its primary exhaust products, carbon dioxide and water . Taking octane , a fairly representative species within the gasoline blend, as an example, the chemical reaction unfolds thus:

2 C 8 H 18 + 25 O 2 → 16 CO 2 + 18 H 2 O

By weight, the combustion of gasoline liberates approximately 46.7 megajoules per kilogram (equivalent to 13.0 kWh /kg, or 21.2 MJ/lb ). When measured by volume, this translates to about 33.6 megajoules per liter (or 9.3 kWh/L; 127 MJ/U.S. gal; 121,000 BTU/U.S. gal), these figures representing the lower heating value . [24] It’s worth noting that gasoline blends are not monolithic; they differ, and consequently, the actual energy content can fluctuate based on the season and the specific producer, exhibiting variations of up to 1.75 percent either above or below the stated average. [25] On average, from a single barrel of crude oil, roughly 74 liters (20 U.S. gal) of gasoline can be extracted, accounting for approximately 46 percent of the total volume. The remaining portion of the barrel yields a diverse array of products, ranging from heavy tar to lighter naphtha . [26]

A fuel boasting a high octane rating , such as liquefied petroleum gas (LPG), will, somewhat counterintuitively, produce a lower overall power output when utilized in an engine designed and optimized for gasoline fuel, typically operating at a 10:1 compression ratio . However, if an engine is specifically tuned for LPG fuel, incorporating higher compression ratios (commonly around 12:1), a notable improvement in power output is achieved. This enhancement arises because higher-octane fuels possess the inherent ability to tolerate a greater compression ratio without succumbing to destructive knocking. This, in turn, permits the attainment of higher cylinder temperatures, which directly translates to an improvement in thermodynamic efficiency . Furthermore, and perhaps more significantly, a higher compression ratio concurrently leads to an increased mechanical efficiency through the associated higher expansion ratio during the power stroke. This greater expansion ratio is the dominant factor, extracting substantially more work from the high-pressure gases generated by the combustion process. Modern innovations like an Atkinson cycle engine ingeniously manipulate valve timing to realize the benefits of a high expansion ratio without incurring the usual disadvantages, primarily the risk of detonation, associated with a high compression ratio. A high expansion ratio is also one of the two foundational reasons for the impressive efficiency observed in diesel engines , the other being the inherent elimination of pumping losses that plague throttled intake airflow systems.

The comparatively lower energy content of LPG when measured by liquid volume, in contrast to gasoline, is predominantly attributable to its lower density. This reduced density is a direct consequence of the lower molecular weight of propane , which constitutes the principal component of LPG, when compared to gasoline’s complex blend of various hydrocarbon compounds, many of which possess significantly heavier molecular weights than propane. Conversely, when considered by weight, LPG’s energy content actually surpasses that of gasoline. This is due to LPG’s more favorable hydrogen -to-carbon ratio, a chemical characteristic that yields more energy per unit mass.

For the chemically inclined, considering the representative octane combustion, the molecular weights of the species involved are as follows: C 8 H 18 (octane) is 114, O 2 (oxygen) is 32, CO 2 (carbon dioxide) is 44, and H 2 O (water) is 18. Therefore, a precise calculation reveals that one kilogram (2.2 lb) of fuel will react with 3.51 kilograms (7.7 lb) of oxygen, ultimately producing 3.09 kilograms (6.8 lb) of carbon dioxide and 1.42 kilograms (3.1 lb) of water. The universe, it seems, balances its books quite meticulously.

Octane rating

For a more exhaustive dive into this subject, one might consult the Main article: Octane rating . One assumes, of course, that the details here are insufficient for your boundless curiosity.

The octane rating is not some arbitrary number; it is a meticulously derived measure, expressed relative to a specific reference mixture. This mixture consists of 2,2,4-trimethylpentane (a particular isomer of octane , known for its excellent anti-knock properties) and n-heptane (a straight-chain alkane, notoriously prone to knocking). It’s important to recognize that various conventions exist for expressing octane ratings, meaning the identical physical fuel might be assigned several different octane values depending on the measurement standard employed. Among these, the Research Octane Number (RON) is perhaps one of the most widely recognized and utilized.

The actual octane rating of commercially available gasoline exhibits considerable variation from one country to another, a rather predictable consequence of differing regulations and market demands. In the Scandinavian nations of Finland , Sweden , and Norway , 95 RON serves as the standard for regular unleaded gasoline, while 98 RON is also readily accessible, albeit as a more premium and thus more expensive option.

Across the United Kingdom , more than 95 percent of all gasoline sold adheres to a 95 RON standard, marketed simply as “Unleaded” or “Premium Unleaded.” The remaining portion of the market is typically comprised of “Super Unleaded,” which offers a 97/98 RON, and various branded high-performance fuels—such as Shell V-Power and BP Ultimate—boasting an impressive 99 RON. For the truly dedicated enthusiast, or perhaps the utterly unhinged, gasoline with a 102 RON might, on rare occasions, be procured for specialized racing purposes. [27] [28] [29]

In the U.S. , octane ratings for unleaded fuels typically range from 85 [30] to 87 AKI (which corresponds to 91–92 RON) for what is considered “regular” grade. “Mid-grade” fuels usually fall between 89–90 AKI (94–95 RON), making them roughly equivalent to European regular gasoline. At the top end, “premium” fuels offer 90–94 AKI (95–99 RON), aligning with European premium offerings.

In South Africa , particularly in its largest city, Johannesburg , which is situated on the Highveld at a considerable elevation of 1,753 meters (5,751 ft) above sea level, the Automobile Association of South Africa (AA) offers a practical recommendation. They suggest using 95-octane gasoline at lower altitudes, but for use in Johannesburg, they advise 93-octane. The rationale is quite logical: “The higher the altitude the lower the air pressure, and the lower the need for a high octane fuel as there is no real performance gain.” [31] One might interpret this as a polite way of saying, “Don’t waste your money where it won’t make a difference.”

The significance of the octane rating escalated dramatically as military strategists, in the late 1920s and throughout the 1940s, relentlessly pursued higher power output for aircraft engines . A superior octane rating is not merely an arbitrary metric; it directly enables the use of a higher compression ratio or increased supercharger boost. These engineering enhancements, in turn, translate into higher operating temperatures and pressures within the engine cylinders, which directly, and quite powerfully, results in a greater power output. Some rather prescient scientists [who?] even went so far as to predict, quite accurately, that any nation possessing a robust supply of high-octane gasoline would gain a decisive advantage in air power. By 1943, the formidable Rolls-Royce Merlin aero engine, a marvel of engineering, was capable of producing 980 kilowatts (1,320 hp) from a relatively modest 27 liters (1,600 cu in) displacement, all thanks to the availability of 100 RON fuel. [32] By the time Operation Overlord was underway, both the RAF and the USAAF were conducting critical operations over Europe utilizing an even more potent 150 RON fuel (specifically 100/150 avgas ), achieved through the addition of a mere 2.5 percent aniline to standard 100-octane avgas. At this zenith of wartime innovation, the Rolls-Royce Merlin 66 engine, a direct descendant of its earlier counterpart, was now developing an astonishing 1,500 kilowatts (2,000 hp) with the aid of this advanced fuel. The lengths to which humanity will go for dominance, even in the air, are truly something to behold.

Additives

For a comprehensive compendium of these chemical interventions, one may refer to the List of gasoline additives .

Antiknock additives

Tetraethyl lead

Gasoline, when subjected to the rigors of high-compression internal combustion engines , possesses an inherent and rather inconvenient tendency to auto-ignite prematurely, or “detonate.” This self-destructive phenomenon results in damaging engine knocking , colloquially known as “pinging” or “pinking,” which is detrimental to engine longevity and performance. To address this persistent engineering challenge, tetraethyl lead (TEL) was, for decades, widely embraced as an additive for gasoline, its use becoming prevalent in the 1920s. However, as awareness of the profound environmental and health damage wrought by lead compounds steadily grew—a rather predictable outcome, one might add—and as the incompatibility of lead with nascent catalytic converters became glaringly apparent, governments worldwide began to implement mandates for significant reductions in gasoline lead content.

In the U.S. , the Environmental Protection Agency (EPA) initiated a series of regulations designed to progressively diminish the lead content of leaded gasoline through annual phases. These regulations were originally slated to commence in 1973 but faced delays due to protracted court appeals, ultimately taking effect in 1976. By 1995, the market share of leaded fuel had dwindled to a mere 0.6 percent of total gasoline sales, with lead emissions plummeting to less than 1,800 metric tons (2,000 short tons; 1,800 long tons) per year. A definitive turning point arrived on January 1, 1996, when the U.S. Clean Air Act unequivocally banned the sale of leaded fuel for use in on-road vehicles throughout the United States. The historical reliance on TEL also necessitated the inclusion of other additives, such as dibromoethane , to facilitate its effective scavenging from the engine.

European countries, following a similar trajectory, began the process of phasing out lead-containing additives by the close of the 1980s. By the end of the 1990s, leaded gasoline was comprehensively banned across the entirety of the European Union , with a notable, if niche, exception for Avgas 100LL used in general aviation . [33] The UAE embarked on its transition to unleaded fuel in the early 2000s, further underscoring the global shift. [34]

In a rather fascinating, and perhaps unexpected, societal outcome, the reduction in the average lead content of human blood has been posited as a significant contributing factor to the observed decline in violent crime rates across the globe, [35] including in nations like South Africa . [36] Indeed, a notable study identified a compelling correlation between the historical usage of leaded gasoline and the prevalence of violent crime, giving rise to what is now known as the Lead–crime hypothesis . [37] [38] Of course, as with all such complex social phenomena, other studies have, perhaps predictably, found no such correlation, leaving the debate open to further, presumably endless, discussion.

In a landmark announcement in August 2021, the UN Environment Programme declared that leaded gasoline had been effectively eradicated worldwide, with Algeria being the last nation to deplete its remaining reserves. UN Secretary-General António Guterres lauded the eradication of leaded petrol as an “international success story,” a rare moment of unequivocal triumph. He further elaborated, stating that “Ending the use of leaded petrol will prevent more than one million premature deaths each year from heart disease, strokes and cancer, and it will protect children whose IQs are damaged by exposure to lead.” Greenpeace , ever vigilant, echoed this sentiment, proclaiming the announcement as “the end of one toxic era.” [39] However, one should not be entirely swayed by such pronouncements of definitive victory. Leaded gasoline, in a testament to humanity’s stubborn adherence to specialized needs, continues to be utilized in aeronautic, auto racing, and various off-road applications. [40] The use of leaded additives remains permissible globally for the formulation of certain grades of aviation gasoline , such as 100LL , precisely because the requisite octane rating for these demanding applications is exceedingly difficult, if not impossible, to achieve without the inclusion of these leaded compounds. A “success story,” perhaps, but not without its footnotes.

In the wake of lead’s departure, a variety of different additives have stepped in to fill the void. The most commonly adopted replacements include various aromatic hydrocarbons , ethers (such as MTBE and ETBE ), and alcohols , with ethanol being the most prevalent.

Lead replacement petrol

Lead replacement petrol (LRP) emerged as a stop-gap solution, specifically engineered for vehicles that were originally designed to operate on leaded fuels and were, by their very nature, incompatible with standard unleaded alternatives. Rather than relying on tetraethyllead , LRP formulations incorporate other metallic compounds, such as those derived from potassium , or methylcyclopentadienyl manganese tricarbonyl (MMT). These compounds were purportedly designed to provide a protective buffering effect to soft exhaust valves and their seats, thereby preventing the recession that would otherwise occur due to the absence of lead in unleaded fuel.

LRP was actively marketed during and immediately following the phaseout of leaded motor fuels in the United Kingdom , Australia , South Africa , and a scattering of other nations. [vague] Curiously, widespread consumer confusion often led to an erroneous preference for LRP over standard unleaded fuel, even in vehicles where it offered no discernible benefit. [41] Consequently, LRP itself was gradually phased out, typically within 8 to 10 years after the initial introduction of unleaded fuels, a testament to the fleeting nature of transitional technologies. [42]

Leaded gasoline was officially withdrawn from sale in Britain after December 31, 1999, a full seven years after EEC regulations had signaled the impending cessation of production for cars designed to run on leaded gasoline in member states. At this juncture, a substantial proportion of vehicles from the 1980s and early 1990s, which were indeed built for leaded fuel, remained in active service, alongside a growing number of cars capable of running on unleaded fuel. However, as the dwindling population of such older vehicles on British roads became increasingly apparent, many gasoline stations, quite logically, began to discontinue LRP sales by 2003, rendering it largely obsolete. [43]

MMT

Methylcyclopentadienyl manganese tricarbonyl (MMT) is employed in Canada and the U.S. as an additive primarily to enhance the octane rating of gasoline. [44] Its use in the United States has been subject to various regulatory restrictions over time, though it is currently permitted under specific conditions. [45] Within the European Union , the application of MMT is more tightly controlled, restricted by Article 8a of the Fuel Quality Directive [46] following extensive testing conducted under the Protocol for the evaluation of effects of metallic fuel-additives on the emissions performance of vehicles. [47] One might deduce that Europe has a slightly healthier skepticism towards adding heavy metals to its fuel.

Fuel stabilizers (antioxidants and metal deactivators)

Substituted phenols and derivatives of phenylenediamine are commonly utilized as antioxidants to effectively inhibit the formation of gum in gasoline.

The rather unpleasant gummy, sticky resin deposits that can plague gasoline are the direct consequence of its oxidative degradation during prolonged storage. These detrimental deposits primarily arise from the oxidation of alkenes and other minor, often reactive, components present in gasoline [citation needed] (a process analogous to what occurs in drying oils ). Fortunately, continuous advancements in refinery techniques have, in general, significantly reduced the inherent susceptibility of modern gasolines to these particular problems. Historically, catalytically or thermally cracked gasolines were the most vulnerable to oxidation. The formation of these gums is, rather inconveniently, accelerated by the presence of copper salts, which can be effectively neutralized by specialized additives known as metal deactivators .

This undesirable degradation can be effectively thwarted through the strategic addition of a small concentration (typically 5–100 ppm) of antioxidants , such as various phenylenediamines and other amines . [11] Hydrocarbons characterized by a bromine number of 10 or higher can be particularly well-protected through the synergistic combination of unhindered or partially hindered phenols and oil-soluble strong amine bases, such as specific hindered phenols. The presence of “stale” gasoline can even be detected through a precise colorimetric enzymatic test designed to identify the organic peroxides that are inevitably produced during the oxidation process of gasoline. [48]

In addition to antioxidants, gasolines are also routinely treated with metal deactivators . These compounds function by sequestering (or deactivating) metal salts that would otherwise act as catalysts, accelerating the formation of those troublesome gummy residues. These metallic impurities can originate either from the engine itself, through wear and tear, or as contaminants introduced within the fuel supply chain. It seems the fight against entropy is a constant one.

Detergents

Gasoline, in its final form as delivered at the pump, is not merely a blend of hydrocarbons; it also contains a precise cocktail of additives specifically designed to mitigate the internal buildup of carbon within the engine, enhance combustion efficiency, and facilitate easier starting in challenging cold climates. Notably high levels of these beneficial detergent additives can be found in what are designated as Top Tier Detergent Gasolines . The stringent specification for these Top Tier fuels was collaboratively developed by four prominent automakers: GM , Honda , Toyota , and BMW . According to a bulletin issued by General Motors, the minimal requirements set by the U.S. EPA are, rather pointedly, deemed insufficient to maintain engine cleanliness effectively. [49] Typical detergents employed in these formulations include alkylamines and alkyl phosphates , usually present at a concentration of 50–100 ppm. [11] It appears even the most basic of fuels requires constant chemical intervention to meet modern demands.

Ethanol

Total corn production (bushels ) (left) Corn used for Ethanol fuel (bushels) (left) Percent of corn used for Ethanol (right)

For an even deeper dive into this particular alcohol , one might consult Ethanol fuel and Common ethanol fuel mixtures .

European Union

This particular segment, it seems, is in need of further corroboration. One might suggest that if the facts aren’t readily available, perhaps they aren’t facts at all. Nevertheless, for those who insist on certainty, verification is apparently required.

Within the European Union , a blend containing up to 5 percent ethanol is permissible under the common gasoline specification (EN 228). However, discussions are perpetually ongoing regarding the allowance of a 10 percent ethanol blend, a formulation that is already commercially available in a selection of Finnish, French, and German gasoline stations. In Finland , for instance, the majority of gasoline stations offer 95E10, which, as the designation implies, contains 10 percent ethanol, alongside 98E5, which has a 5 percent ethanol content. Much of the gasoline retailed in Sweden also incorporates between 5 and 15 percent ethanol. In the Netherlands , a rather diverse array of three different ethanol blends is available to consumers: E5, E10, and hE15. The latter, hE15, distinguishes itself from conventional ethanol-gasoline blends by comprising 15 percent hydrous ethanol —meaning the ethanol–water azeotrope —rather than the anhydrous ethanol traditionally favored for blending with gasoline.

Between 2009 and 2022, the mandated renewable percentage in gasoline within the EU saw a gradual increase, climbing from 5% to 10%. This progression occurred despite the fact that EU-produced ethanol is capable of achieving climate-neutral production, and a significant proportion of EU cars are technically capable of utilizing E10 fuel. Yet, curiously, E10 availability remains conspicuously low, even in larger countries such as Germany (where it stands at a mere 26%) and France (at 58%). As of 2024, a notable eight countries within the EU have yet to fully adopt E10. [50] One might infer that progress, much like humanity itself, moves at its own rather glacial pace.

Brazil

The Brazilian National Agency of Petroleum, Natural Gas and Biofuels (ANP), with its rather comprehensive mandate, requires that gasoline designated for automobile use must contain a substantial 27.5 percent of ethanol in its composition. [51] Furthermore, pure hydrated ethanol is also readily available as a direct fuel source, offering consumers a choice in their propulsion methods.

Australia

For a more detailed exposition on this topic, one might consult Biofuel in Australia .

Australia embraces both E10 (containing up to 10% ethanol) and E85 (featuring up to 85% ethanol) within its gasoline market. New South Wales took a legislative stance, mandating biofuel usage through its Biofuels Act 2007, while Queensland followed suit with its own biofuel mandate, in effect since 2017. To ensure transparency for consumers, all fuel pumps are legally required to be conspicuously labeled with their precise ethanol or biodiesel content. [52] It seems even the land down under can’t escape the complexities of fuel blends.

U.S.

This particular section, it appears, suffers from a rather unfortunate lack of evidentiary support. One might suggest that if one is to make claims, one should perhaps provide some form of citation from a reliable source . Until such time, the material may be removed . (September 2024) One can only patiently await the arrival of the facts.

The federal Renewable Fuel Standard (RFS) in the U.S. effectively compels refiners and blenders to incorporate renewable biofuels —primarily ethanol —into gasoline. This is not a suggestion, but a requirement, designed to meet an annually escalating target for the total gallons blended. While the mandate itself refrains from stipulating a precise percentage of ethanol, the cumulative effect of these annual increases, combined with a gradual decline in overall gasoline consumption , has resulted in the typical ethanol content in gasoline gravitating towards the 10 percent mark. Most fuel pumps, with a curious nod to legalistic precision, display a sticker indicating that the fuel “may contain up to 10 percent ethanol,” a deliberate disparity that merely reflects the varying actual percentage present. In certain regions of the U.S., ethanol is sometimes added to gasoline without any explicit indication of its presence, a subtle act of omission that one might find either convenient or vaguely unsettling.

India

In October 2007, the Government of India made a rather significant decision, mandating a five percent ethanol blend (with gasoline) across the nation. Currently, a 10 percent ethanol blended product (E10) is widely available and sold in various parts of the country. [53] [54] It has been noted, in at least one study, that ethanol can, rather inconveniently, cause damage to catalytic converters . [55] Looking ahead, by July 2025, India has further mandated the blending of E20, a decision that has, predictably, met with considerable backlash. [56] [57] One might observe that the path to greener fuels is rarely smooth, or indeed, universally applauded.

Dyes

For a more colorful exposition on this topic, one might consult the Main article: Fuel dyes .

Although gasoline is, in its pristine natural state, a perfectly colorless liquid, many commercial gasolines are deliberately dyed in a spectrum of various colors. This chromatic coding serves a dual purpose: to clearly indicate their specific chemical composition and to delineate their acceptable uses, thereby preventing confusion and misuse. In Australia , for example, the lowest grade of gasoline (RON 91) was historically dyed a distinctive light shade of red or orange. However, this practice has since been abandoned, and it now shares the same yellow hue as both the medium grade (RON 95) and the high-octane (RON 98) variants. [58] In the U.S. , aviation gasoline is meticulously dyed to clearly identify its octane rating and, crucially, to distinguish it from kerosene-based jet fuel , which is typically left colorless. [59] Across Canada , gasoline intended for marine and farm use is conspicuously dyed red. This distinctive coloring serves a practical purpose: it signifies that this particular fuel is exempt from fuel excise tax in most provinces, a fiscal concession for specific applications. [60]

Oxygenate blending

The practice of oxygenate blending involves the deliberate addition of oxygen-bearing compounds, such as methanol , MTBE , ETBE , TAME , TAEE , ethanol , and biobutanol , to gasoline. The primary objective behind the inclusion of these oxygenates is to reduce the emission of carbon monoxide and unburned fuel from vehicle exhaust, thereby improving air quality. In numerous regions throughout the U.S. , oxygenate blending is not merely optional but is mandated by EPA regulations, specifically to combat smog and other airborne pollutants. For instance, in Southern California, fuel is legally required to contain two percent oxygen by weight, a specification typically met by a mixture of 5.6 percent ethanol in gasoline. The resultant fuel is often generically referred to as reformulated gasoline (RFG) or oxygenated gasoline, or, in the specific case of California , California reformulated gasoline (CARBOB). Curiously, the federal requirement for RFG to contain oxygen was eventually dropped on May 6, 2006, as the industry successfully developed VOC -controlled RFG formulations that no longer necessitated the addition of supplementary oxygen. [61]

MTBE , once a widespread oxygenate, was progressively phased out in the U.S. due to mounting concerns over groundwater contamination and the subsequent cascade of regulatory actions and lawsuits. Ethanol and, to a lesser extent, the ethanol-derived ETBE , have emerged as common substitutes, stepping into the void left by MTBE. A widely adopted ethanol-gasoline mixture, comprising 10 percent ethanol blended with gasoline, is popularly known as gasohol or E10. For those seeking a higher concentration, an ethanol-gasoline mix containing 85 percent ethanol is designated as E85 . The most extensive and integrated use of ethanol as a fuel takes place in Brazil , where the ethanol is efficiently derived from readily available sugarcane . In 2004, over 13 billion liters (3.4×10^9 U.S. gal) of ethanol were produced in the U.S. specifically for fuel use, predominantly sourced from corn and subsequently sold as E10. E85, while slowly gaining traction, remains less ubiquitous, with many of the relatively few stations vending it not always accessible to the general public. [62]

The utilization of bioethanol and bio-methanol, whether directly or indirectly through the conversion of ethanol to bio-ETBE or methanol to bio-MTBE, is actively encouraged by the European Union ’s Directive on the Promotion of the use of biofuels and other renewable fuels for transport . However, a rather ironic twist exists: since the production of bioethanol from fermented sugars and starches necessarily involves distillation , ordinary citizens in much of Europe are currently legally prohibited from fermenting and distilling their own bioethanol. This stands in stark contrast to the U.S. , where obtaining a BATF distillation permit has been a comparatively straightforward process since the 1973 oil crisis , a situation that one might find either amusing or deeply frustrating, depending on one’s perspective.

Safety

One might imagine that a highly flammable, complex chemical cocktail is not entirely benign. And one would, of course, be correct.

Toxicity

The safety data sheet for a representative 2003 Texan unleaded gasoline reveals a rather concerning list of at least 15 hazardous chemicals, present in varying concentrations. These include benzene (up to five percent by volume), toluene (up to 35 percent by volume), naphthalene (up to one percent by volume), trimethylbenzene (up to seven percent by volume), methyl tert-butyl ether (MTBE) (up to 18 percent by volume, in some states), and approximately ten other compounds. [63] While the general collection of hydrocarbons found in gasoline typically exhibits low acute toxicities, with LD 50 values ranging from 700–2700 mg/kg for simpler aromatic compounds, [64] it is crucial to recognize that benzene and many of the historical anti-knocking additives are unequivocally carcinogenic .

Individuals can be exposed to gasoline in various workplace settings through multiple routes: ingestion, inhalation of vapors, direct skin contact, and eye contact. Gasoline is, without equivocation, toxic. The National Institute for Occupational Safety and Health (NIOSH) has, quite rightly, designated gasoline as a carcinogen. [65] Any physical contact, accidental ingestion, or inhalation can precipitate a range of health problems. Ingesting substantial quantities of gasoline can lead to permanent damage to major organs, necessitating an immediate call to a local poison control center or an emergency room visit. [66]

However, contrary to a rather persistent common misconception , the accidental swallowing of gasoline does not generally require specialized emergency treatment, and, perhaps more importantly, inducing vomiting is not only unhelpful but can, in fact, exacerbate the situation. According to poison specialist Brad Dahl, “even two mouthfuls wouldn’t be that dangerous as long as it goes down to your stomach and stays there or keeps going.” The U.S. CDC ’s Agency for Toxic Substances and Disease Registry explicitly advises against inducing vomiting, performing lavage , or administering activated charcoal in such cases. [67] [68] One might infer that common sense, in these situations, is far less common than one would hope.

Inhalation for intoxication

The deliberate inhalation (or “huffing”) of gasoline vapor is, unfortunately, a tragically common method of intoxication. Users intentionally concentrate and inhale gasoline vapor in a manner entirely unintended by the manufacturer, seeking to induce feelings of euphoria and intoxication . This practice has escalated to epidemic proportions in certain impoverished communities and among indigenous groups in Australia , Canada , New Zealand , and some Pacific Islands. [69] The inhalation of gasoline is widely understood to cause severe and often irreversible organ damage, alongside a litany of other devastating effects, including intellectual disability and various forms of cancers . [70] [71] [72] [73]

In Canada , the plight of Native children in the isolated Northern Labrador community of Davis Inlet garnered national attention in 1993, when a significant number were discovered to be sniffing gasoline. Both the Canadian federal and provincial Newfoundland and Labrador governments intervened on multiple occasions, sending many of these children away for treatment. Despite the community’s relocation to the newly established settlement of Natuashish in 2002, severe inhalant abuse problems have, tragically, persisted. Similar issues were reported in Sheshatshiu in 2000 and subsequently in Pikangikum First Nation . [74] The issue, with a depressingly predictable regularity, once again seized the attention of the news media in Canada in 2012. [75]

For further insights into substance abuse within indigenous communities, one might consult Indigenous Australian § Substance abuse .

Australia has, for a considerable period, grappled with a deeply entrenched petrol (gasoline) sniffing problem, particularly prevalent in its isolated and impoverished aboriginal communities. While some sources contend that the practice of sniffing was introduced by U.S. servicemen stationed in the nation’s Top End during World War II [76] or through early experimentation by 1940s-era Cobourg Peninsula sawmill workers, [77] other accounts suggest that inhalant abuse, including substances like glue, first emerged in Australia in the late 1960s. [78] Chronic, heavy petrol sniffing appears to be concentrated among remote, economically disadvantaged indigenous communities, where the ready and often unavoidable accessibility of petrol has, unfortunately, contributed to its widespread use as a substance of abuse.

Currently, petrol sniffing is a pervasive issue throughout remote Aboriginal communities spanning the Northern Territory , Western Australia , the northern reaches of South Australia , and Queensland . [79] The number of individuals engaging in petrol sniffing fluctuates over time, reflecting the transient nature of youthful experimentation or occasional use. However, “Boss” sniffers, typically chronic users, often migrate between communities, and are frequently identified as instrumental in encouraging younger individuals to adopt the practice, perpetuating a grim cycle. [80] In a proactive response, in 2005, the Government of Australia and BP Australia initiated the introduction of Opal fuel in remote areas particularly susceptible to petrol sniffing. [81] Opal is specifically formulated as a non-sniffable fuel, meaning it is significantly less likely to induce the desired “high,” and its introduction has demonstrably made a positive difference in several indigenous communities, offering a glimmer of hope in a challenging situation.

Flammability

The uncontrolled combustion of gasoline, a rather common occurrence in accidents, regrettably generates substantial quantities of noxious soot and deadly carbon monoxide .

Gasoline is inherently flammable , characterized by a remarkably low flash point of −23 °C (−9 °F). This low flash point means it can easily ignite even at very cold temperatures. The precise conditions for ignition are also governed by its explosive limits: gasoline possesses a lower explosive limit of 1.4 percent by volume and an upper explosive limit of 7.6 percent. Should the concentration of gasoline vapor in the air fall below 1.4 percent, the air-gasoline mixture is deemed too lean and will, quite simply, not ignite. Conversely, if the concentration rises above 7.6 percent, the mixture becomes too rich and, again, will not ignite. However, it is crucial to understand that gasoline vapor, being volatile, rapidly mixes and disperses within the air, rendering unconstrained gasoline an extremely and quickly flammable substance. One might say it’s quite eager to fulfill its destructive potential.

Gasoline exhaust

The exhaust gas expelled from the combustion of gasoline is, unequivocally, detrimental to both the delicate balance of the environment and the fragile health of human beings. Once carbon monoxide (CO) is inhaled into the human body, it exhibits a disturbingly high affinity for hemoglobin in the blood, an affinity approximately 300 times greater than that of oxygen. Consequently, the hemoglobin molecules within the lungs preferentially bind with CO instead of vital oxygen, leading to a state of hypoxia (oxygen deprivation) throughout the human body. This insidious process manifests in a cascade of poisoning symptoms, including headaches, dizziness, and vomiting. In severe cases, this deprivation can, quite tragically, culminate in death. [82] [83]

Hydrocarbons, another component of exhaust, only begin to exert their deleterious effects on the human body when their concentration reaches rather elevated levels, with their precise toxicity contingent upon their specific chemical composition. The hydrocarbons produced by incomplete combustion processes encompass alkanes , aromatics , and aldehydes . Among these, a concentration of methane and ethane exceeding 35 g/m³ (0.035 oz/cu ft) can induce a loss of consciousness or, more severely, suffocation. Pentane and hexane, when present at concentrations above 45 g/m³ (0.045 oz/cu ft), can exert an anesthetic effect. Aromatic hydrocarbons, however, pose more significant health risks, contributing to blood toxicity, neurotoxicity , and, most disturbingly, cancer. For instance, if the concentration of benzene surpasses 40 ppm, it can lead to the development of leukaemia , while xylene exposure can cause headaches, dizziness, nausea, and vomiting. Human exposure to large quantities of aldehydes can trigger eye irritation, nausea, and dizziness. Beyond their immediate effects, long-term exposure to aldehydes can also result in skin damage, liver and kidney damage, and the formation of cataracts. [84]

Nitrogen oxides (NOx), upon entering the alveoli of the lungs, exert a severe irritating effect on the lung tissue. They can also irritate the conjunctiva of the eyes, causing tearing and leading to “pink eye.” Furthermore, NOx has a stimulating effect on the nose, pharynx, throat, and other respiratory organs, potentially causing acute wheezing, breathing difficulties, red eyes, a sore throat, and dizziness, all indicative of poisoning. [84] [85] And, as if that weren’t enough, fine particulates , often invisible to the naked eye, also pose a significant danger to human health. [86] One might conclude that gasoline exhaust is not, in fact, a health tonic.

Environmental effect

The very character of air pollution in many of our sprawling urban centers has undergone a rather unwelcome metamorphosis, shifting from the historical scourge of coal-burning pollution to the pervasive, modern problem of “motor vehicle pollution.” In the U.S. , transportation stands as the single largest progenitor of carbon emissions, accounting for a staggering 30 percent of the nation’s total carbon footprint. [87] The combustion of a mere liter of gasoline releases approximately 2.35 kilograms (19.6 lb/U.S. gal) of carbon dioxide , a potent greenhouse gas , into the atmosphere. [88] [89] One might observe that our collective reliance on this liquid comes at a rather steep price.

Unburnt gasoline and the often-overlooked evaporation from the tank , once released into the atmosphere , undergo complex photochemical reactions when exposed to sunlight , culminating in the formation of photochemical smog . Interestingly, the vapor pressure of gasoline initially increases with the addition of some ethanol , with the most significant increase observed at approximately 10 percent by volume. [90] However, at higher concentrations of ethanol beyond 10 percent, the vapor pressure of the blend begins to decrease. This initial rise in vapor pressure at the 10 percent ethanol mark could, potentially, exacerbate the problem of photochemical smog. Fortunately, this increase in vapor pressure can be mitigated by either increasing or decreasing the percentage of ethanol in the gasoline mixture, a delicate balancing act. The primary environmental risks associated with gasoline leaks, it turns out, do not predominantly stem from individual vehicles, but rather from more substantial incidents such as gasoline delivery truck accidents and chronic leaks from underground storage tanks. Recognizing this significant risk, most (underground) storage tanks are now equipped with extensive measures designed to detect and prevent such leaks, incorporating sophisticated monitoring systems (e.g., Veeder-Root, Franklin Fueling).

The production of gasoline is also a surprisingly thirsty process, consuming approximately 1.5 liters of water for every kilometer (0.63 U.S. gal/mi) driven. [91]

The widespread use of gasoline inflicts a multitude of deleterious effects upon the human population and, indeed, upon the global climate system as a whole. The harms imposed are extensive and varied, including a heightened rate of premature mortality and a proliferation of ailments such as asthma , all directly attributable to air pollution . This translates into elevated healthcare costs for the public at large, diminished crop yields , an increase in missed work and school days due to illness, and the unsettling rise in flooding and other extreme weather events inextricably linked to global climate change . These, among other societal costs, are often externalized, meaning they are not reflected in the price at the pump. The estimated social cost imposed on society and the planet is a sobering $3.80 per gallon of gasoline, a figure that exists in addition to the price paid by the user. It is clear that the damage inflicted upon both human health and the climate by a gasoline-powered vehicle substantially exceeds that caused by its electric counterparts. [92] [93]

Gasoline, in its various forms, can be inadvertently released into the environment as an uncombusted liquid fuel, as a highly flammable liquid, or as a volatile vapor. These releases typically occur through leakages at various stages of its production, handling, transport, and delivery. [94] Gasoline contains known carcinogens , [95] [96] [97] and its exhaust is, without question, a significant health risk. [86] Moreover, gasoline is, regrettably, often misused as a recreational inhalant , a practice that can be severely harmful or even fatal. [98] When combusted, a single liter (0.26 U.S. gal) of gasoline emits approximately 2.3 kilograms (5.1 lb) of CO 2 , a potent greenhouse gas , thereby contributing directly to human-caused climate change . [99] [100] It is estimated that oil products, including gasoline, were responsible for roughly 32% of all CO 2 emissions worldwide in 2021. [101]

Carbon dioxide

Approximately 2.353 kilograms per liter (19.64 lb/U.S. gal) of carbon dioxide (CO 2 ) are produced from the combustion of gasoline that does not contain ethanol . [89] However, the majority of retail gasoline currently sold in the U.S. now contains about 10 percent fuel ethanol (or E10) by volume. [89] When E10 is combusted, approximately 2.119 kilograms per liter (17.68 lb/U.S. gal) of CO 2 are emitted specifically from its fossil fuel content. If one were to also consider the CO 2 emissions derived from the combustion of the ethanol component, then the total figure for E10 combustion rises to about 2.271 kilograms per liter (18.95 lb/U.S. gal) of CO 2 . [89] One might perceive this as a slight improvement, or merely a statistical sleight of hand, depending on one’s perspective.

Globally, an average of 7 liters of gasoline are consumed for every 100 kilometers driven by cars and vans, a rather significant expenditure of resources. [102]

In 2021, the International Energy Agency (IEA) issued a rather pointed statement, asserting that “To ensure fuel economy and CO 2 emissions standards are effective, governments must continue regulatory efforts to monitor and reduce the gap between real-world fuel economy and rated performance.” [102] A polite way of saying, “Stop fudging the numbers.”

Contamination of soil and water

Gasoline, with its inherent volatility and toxicity, finds its way into the environment through various pathways: the soil, groundwater, surface water bodies, and the ambient air. Consequently, human beings can be exposed to gasoline through multiple means, including respiration, ingestion, and direct skin contact. For instance, common activities such as operating gasoline-fueled equipment like lawnmowers, consuming water that has become contaminated by gasoline spills or leaks into the soil, working at a gasoline station, or even merely inhaling volatile gasoline fumes while refueling a vehicle are all readily identifiable avenues of exposure. [103] It seems, then, that one cannot entirely escape its pervasive presence.

Use and pricing

For an exhaustive analysis of the economic landscape surrounding this fuel, one might consult the Main articles: Gasoline and diesel usage and pricing and Peak oil .

The International Energy Agency (IEA) stated, with a rather direct tone, in 2021 that “road fuels should be taxed at a rate that reflects their impact on people’s health and the climate.” [102] A novel concept, perhaps, for some.

Europe

Countries across Europe consistently levy substantially higher taxes on fuels such as gasoline when compared to the U.S. . This significant disparity in taxation is the primary reason why the price of gasoline in Europe is typically, and rather predictably, higher than that observed in the United States. [104] One might argue it’s a cost of living in a society that attempts to account for externalities.

U.S.

This particular section, it appears, is in dire need of an update. One might suggest that if the information is no longer current, it ceases to be entirely useful. Please assist in bringing this article into the present by reflecting recent events or newly available information. (April 2016) Time, it seems, waits for no Wikipedia article.

RBOB Gasoline Prices RBOB plus excise taxes on gasoline reflect prices paid at the pump

Between the years 1998 and 2004, the price of gasoline in the U.S. exhibited a degree of fluctuation, hovering between $0.26 and $0.53 per liter ($1 and $2/U.S. gal). [105] However, following 2004, prices embarked on a steady upward trajectory, culminating in the national average gasoline price reaching a peak of $1.09 per liter ($4.11/U.S. gal) in mid-2008. This surge was, however, followed by a recession, with prices receding to approximately $0.69 per liter ($2.60/U.S. gal) by September 2009. [105] The U.S. then experienced another significant upswing in gasoline prices throughout 2011, [106] and by March 1, 2012, the national average had reached $0.99 per liter ($3.74/U.S. gal). It is worth noting that prices in California consistently remain higher than the national average. This is primarily due to the state government’s mandate for unique California gasoline formulas, which are more costly to produce, coupled with higher state taxes. [107]

In the U.S. , it is a peculiar convention that most consumer goods display pre-tax prices, necessitating the calculation of tax at the point of sale. Gasoline, however, operates under a different paradigm: its prices are invariably posted with all applicable taxes already included. These taxes are levied by a trifecta of governmental bodies: federal, state, and local entities. As of 2009 [update] , the federal tax stood at $0.049 per liter ($0.184/U.S. gal) for gasoline and $0.064 per liter ($0.244/U.S. gal) for diesel (excluding red diesel , which is typically used off-road). [108]

According to the Energy Information Administration, approximately nine percent of all gasoline sold in the U.S. in May 2009 was of the premium grade. Consumer Reports magazine, in a rather blunt assessment, advises consumers: “If [your owner’s manual] says to use regular fuel, do so—there’s no advantage to a higher grade.” [109] The Associated Press echoed this sentiment, stating that premium gas—which boasts a higher octane rating and consequently costs more per gallon than regular unleaded—should only be used if the manufacturer explicitly states it is “required.” [110] However, it is not simply a matter of preference. Cars equipped with turbocharged engines and high compression ratios frequently specify premium gasoline because higher octane fuels demonstrably reduce the incidence of “knock,” or fuel pre-detonation, thereby protecting the engine and optimizing performance. [111] Furthermore, the price of gasoline exhibits a considerable and rather predictable variation between the summer and winter months, a reflection of differing fuel formulations. [112]

This seasonal variation is primarily driven by a significant difference in gasoline vapor pressure (specifically, Reid Vapor Pressure, or RVP) between summer and winter blends. RVP serves as a critical measure of how readily the fuel evaporates at a given temperature. The higher the gasoline’s volatility (i.e., the higher its RVP), the more easily it evaporates. The transition between these two distinct fuel formulations typically occurs twice annually: once in autumn for the winter mix, and again in spring for the summer mix. The winter blended fuel is engineered with a higher RVP, a necessary characteristic that ensures the fuel can evaporate sufficiently at lower ambient temperatures, allowing the engine to start and run normally. If the RVP were too low on a cold day, vehicles would be notoriously difficult to start. Conversely, summer blended gasoline is formulated with a lower RVP. This reduced volatility is crucial for preventing excessive evaporation when outdoor temperatures rise, thereby helping to curb ozone emissions and reduce overall smog levels. Concurrently, a lower RVP in warmer weather also significantly reduces the likelihood of vapor lock, a condition where fuel vaporizes in the lines, disrupting fuel flow and causing engine stalling. [113] One might appreciate the elegant, if somewhat tedious, engineering behind such seemingly mundane necessities.

Gasoline production by country

For those who enjoy a global perspective on industrial output, this table offers a rather stark overview. [114]

Comparison with other fuels

This segment, it appears, is also in need of further corroboration. One might suggest that if one is to make comparisons, one should perhaps provide some form of citation from a reliable source . Until such time, the material may be challenged and removed. (December 2020) For a more comprehensive look at energy content, one might consult Energy content of biofuel .

Below is a table offering a comparative overview of the energy density (per volume) and specific energy (per mass) of various transportation fuels, juxtaposed against gasoline. The data presented in the rows labeled “Gross” and “Net” are sourced from the Oak Ridge National Laboratory ’s Transportation Energy Data Book. [115] One might find these figures illuminating, or merely another set of numbers to ponder.

| Fuel type | Energy density