The fuel-characteristics of a particular gasoline-blend, which will resist igniting too early are measured as theoctane rating of the fuel blend. Gasoline blends with stable octane ratings are produced in several fuel-grades for various types of motors. A low octane rated fuel may causeengine knocking and reduced efficiency inreciprocating engines.Tetraethyl lead was once widely used to increase the octane rating but is not used in modern automotive gasoline due to thehealth hazard. Aviation, off-road motor vehicles, andracing car motors still use leaded gasolines.[2][3]
English dictionaries show that the termgasoline originates fromgas plus the chemical suffixes-ole and-ine.[4][5][6]Petrol derives from theMedieval Latin wordpetroleum (L.petra, rock +oleum, oil).[7]
Interest in gasoline-like fuels started with the invention of internal combustion engines suitable for use in transportation applications. The so-calledOtto engines were developed in Germany during the last quarter of the 19th century. The fuel for these early engines was a relatively volatilehydrocarbon obtained fromcoal gas. With aboiling point near 85 °C (185 °F) (n-octane boils at 125.62 °C (258.12 °F)[8]), it was well suited for earlycarburetors (evaporators). The development of a "spray nozzle" carburetor enabled the use of less volatile fuels. Further improvements in engine efficiency were attempted at highercompression ratios, but early attempts were blocked by the premature explosion of fuel, known asknocking. In 1891, theShukhov cracking process became the world's first commercial method to break down heavier hydrocarbons in crude oil to increase the percentage of lighter products compared to simple distillation.
Commercial gasoline as well as other liquid transportation fuels are complex mixtures of hydrocarbons.[9] The performance specification also varies with season, requiring less volatile blends during summer, in order to minimize evaporative losses.
Gasoline is produced inoil refineries. Roughly 72 liters (19 U.S. gal) of gasoline is derived from a 160-liter (42 U.S. gal) barrel ofcrude oil.[10] Material separated from crude oil viadistillation, called virgin or straight-run gasoline, does not meet specifications for modern engines (particularly theoctane rating; see below), but can be pooled to the gasoline blend.
The bulk of a typical gasoline consists of a homogeneous mixture ofhydrocarbons with between four and twelvecarbon atoms per molecule (commonly referred to as C4–C12).[11] It is a mixture of paraffins (alkanes), olefins (alkenes), napthenes (cycloalkanes), andaromatics. The use of the termparaffin in place of the standard chemical nomenclaturealkane is particular to the oil industry (which relies extensively on jargon). The composition of a gasoline depends upon:
the oil refinery that makes the gasoline, as not all refineries have the same set of processing units;
the grade of gasoline sought (in particular, the octane rating).
The various refinery streams blended to make gasoline have different characteristics. Some important streams include the following:
Straight-run gasoline, sometimes referred to asnaphtha (and also light straight run naphtha "LSR" and light virgin naphtha "LVN"), is distilled directly from crude oil. Once the leading source of fuel, naphtha's low octane rating required organometallic fuel additives (primarilytetraethyllead) prior to their phaseout from the gasoline pool which started in 1975 in the United States.[12] Straight run naphtha is typically low in aromatics (depending on the grade of the crude oil stream) and contains some cycloalkanes (naphthenes) and no olefins (alkenes). Between 0 and 20 percent of this stream is pooled into the finished gasoline because the quantity of this fraction in the crude is less than fuel demand and the fraction'sResearch Octane Number (RON) is too low. The chemical properties (namely RON andReid vapor pressure (RVP)) of the straight-run gasoline can be improved throughreforming andisomerization. However, before feeding those units, the naphtha needs to be split into light and heavy naphtha. Straight-run gasoline can also be used as a feedstock for steam-crackers to produce olefins.
Reformate, produced from straight run gasoline in acatalytic reformer, has a high octane rating with high aromatic content and relatively low olefin content. Most of thebenzene,toluene, andxylene (the so-calledBTX hydrocarbons) are more valuable as chemical feedstocks and are thus removed to some extent. Also the BTX content is regulated.
Catalytic cracked gasoline, or catalytic crackednaphtha, produced with acatalytic cracker, has a moderate octane rating, high olefin content, and moderate aromatic content.
Hydrocrackate (heavy, mid, and light), produced with ahydrocracker, has a medium to low octane rating and moderate aromatic levels.
Alkylate is produced in analkylation unit, usingisobutane and C3-/C4-olefins as feedstocks. Finished alkylate contains no aromatics or olefins and has a high MON (Motor Octane Number) Alkylate was used during world war 2 inaviation fuel.[13] Since the late 1980s it is sold as a specialty fuel for (handheld) gardening and forestry tools with a combustion engine.[14][15]
Isomerate is obtained by isomerizing low-octane straight-run gasoline into iso-paraffins (non-chain alkanes, such asisooctane). Isomerate has a medium RON and MON, but no aromatics or olefins.
Butane is usually blended in the gasoline pool, although the quantity of this stream is limited by the RVP specification.
Oxygenates (more specificallyalcohols andesters) are mostly blended into the pool in the US asethanol. In Europe and other countries, the blends can containethanol in addition toMethyl tertiary-butyl ether (MTBE) andEthyl tert-butyl ether (ETBE). MTBE in the United States was banned by most states in the early to mid 2000s.[16] A few countries still allowmethanol as well to be blended directly into gasoline, especially in China.[17] More about oxygenates and blending is covered further in this article.
The terms above are the jargon used in the oil industry, and the terminology varies.
Currently, many countries set limits on gasolinearomatics in general, benzene in particular, and olefin (alkene) content. Such regulations have led to an increasing preference for alkane isomers, such as isomerate or alkylate, as their octane rating is higher than n-alkanes. In the European Union, the benzene limit is set at one percent by volume for all grades of automotive gasoline. This is usually achieved by avoiding feeding C6, in particularcyclohexane, to the reformer unit, where it would be converted to benzene. Therefore, only (desulfurized) heavy virgin naphtha (HVN) is fed to the reformer unit[18]
Gasoline can also contain otherorganic compounds, such asorganic ethers (deliberately added), plus small levels of contaminants, in particularorganosulfur compounds (which are usually removed at the refinery).
On average, U.S. petroleum refineries produce about 19 to 20 gallons of gasoline, 11 to 13 gallons of distillate fueldiesel fuel and 3 to 4 gallons ofjet fuel from each 42 U.S. gallons (160 liters)barrel ofcrude oil. The product ratio depends upon the processing in anoil refinery and thecrude oil assay.[19]
Thespecific gravity of gasoline ranges from 0.71 to 0.77,[20] with higher densities having a greater volume fraction of aromatics.[21] Finished marketable gasoline is traded (in Europe) with a standard reference of 0.755 kilograms per liter (6.30 lb/U.S. gal), (7,5668 lb/ imp gal) its price is escalated or de-escalated according to its actual density.[clarification needed] Because of its low density, gasoline floats on water, and therefore water cannot generally be used to extinguish a gasoline fire unless applied in a fine mist.
Quality gasoline should bestable for six months if stored properly, but can degrade over time.[22] Gasoline stored for a year will most likely be able to be burned in an internal combustion engine without too much trouble.[22] Gasoline should ideally be stored in an airtight container (to preventoxidation or water vapor mixing in with the gas) that can withstand thevapor pressure of the gasoline without venting (to prevent the loss of the more volatile fractions) at a stable cool temperature (to reduce the excess pressure from liquid expansion and to reduce the rate of any decomposition reactions). When gasoline is not stored correctly, gums and solids may result, which can corrode system components and accumulate on wet surfaces, resulting in a condition called "stale fuel". Gasoline containing ethanol is especially subject to absorbing atmospheric moisture, then forming gums, solids, or two phases (a hydrocarbon phase floating on top of a water-alcohol phase).[22]
The presence of these degradation products in the fuel tank or fuel lines plus a carburetor or fuel injection components makes it harder to start the engine or causes reduced engine performance[23] On resumption of regular engine use, the buildup may or may not be eventually cleaned out by the flow of fresh gasoline. The addition of a fuel stabilizer to gasoline can extend the life of fuel that is not or cannot be stored properly, though removal of all fuel from a fuel system is the only real solution to the problem of long-term storage of an engine or a machine or vehicle. Typical fuel stabilizers are proprietary mixtures containingmineral spirits,isopropyl alcohol,1,2,4-trimethylbenzene orother additives. Fuel stabilizers are commonly used for small engines, such as lawnmower and tractor engines, especially when their use is sporadic or seasonal (little to no use for one or more seasons of the year). Users have been advised to keep gasoline containers more than half full and properly capped to reduce air exposure, to avoid storage at high temperatures, to run an engine for ten minutes to circulate the stabilizer through all components prior to storage, and to run the engine at intervals to purge stale fuel from the carburetor.[11]
Gasoline stability requirements are set by the standardASTM D4814. This standard describes the various characteristics and requirements of automotive fuels for use over a wide range of operating conditions in ground vehicles equipped with spark-ignition engines.
A gasoline-fueled internal combustion engine obtains energy from thecombustion of gasoline's various hydrocarbons withoxygen from the ambient air, yieldingcarbon dioxide andwater as exhaust. The combustion ofoctane, a representative species, performs the chemical reaction:
2 C8H18 + 25 O2 → 16 CO2 + 18 H2O
By weight, combustion of gasoline releases about 46.7megajoules perkilogram (13.0 kWh/kg; 21.2 MJ/lb) or by volume 33.6megajoules perliter (9.3 kWh/L; 127 MJ/U.S. gal; 121,000 BTU/U.S. gal), quoting thelower heating value.[24] Gasoline blends differ, and therefore actual energy content varies according to the season and producer by up to 1.75 percent more or less than the average.[25] On average, about 74 liters (20 U.S. gal) of gasoline are available from a barrel of crude oil (about 46 percent by volume), varying with the quality of the crude and the grade of the gasoline. The remainder is products ranging from tar tonaphtha.[26]
A high-octane-rated fuel, such asliquefied petroleum gas (LPG), has an overall lower power output at the typical 10:1compression ratio of an engine design optimized for gasoline fuel. An enginetuned forLPG fuel via higher compression ratios (typically 12:1) improves the power output. This is because higher-octane fuels allow for a higher compression ratio without knocking, resulting in a higher cylinder temperature, which improvesefficiency. Also, increased mechanical efficiency is created by a higher compression ratio through the concomitant higher expansion ratio on the power stroke, which is by far the greater effect. The higher expansion ratio extracts more work from the high-pressure gas created by the combustion process. AnAtkinson cycle engine uses the timing of the valve events to produce the benefits of a high expansion ratio without the disadvantages, chiefly detonation, of a high compression ratio. A high expansion ratio is also one of the two key reasons for the efficiency ofdiesel engines, along with the elimination of pumping losses due to throttling of the intake airflow.
The lower energy content of LPG by liquid volume in comparison to gasoline is due mainly to its lower density. This lower density is a property of the lowermolecular weight ofpropane (LPG's chief component) compared to gasoline's blend of various hydrocarbon compounds with heavier molecular weights than propane. Conversely, LPG's energy content by weight is higher than gasoline's due to a higherhydrogen-to-carbon ratio.
Molecular weights of the species in the representative octane combustion are 114, 32, 44, and 18 for C8H18, O2, CO2, and H2O, respectively; therefore one kilogram (2.2 lb) of fuel reacts with 3.51 kilograms (7.7 lb) of oxygen to produce 3.09 kilograms (6.8 lb) of carbon dioxide and 1.42 kilograms (3.1 lb) of water.
Spark-ignition engines are designed to burn gasoline in a controlled process calleddeflagration. However, the unburned mixture may autoignite by pressure and heat alone, rather than igniting from thespark plug at exactly the right time, causing a rapid pressure rise that can damage the engine. This is often referred to asengine knocking or end-gas knock. Knocking can be reduced by increasing the gasoline's resistance toautoignition, which is expressed by its octane rating. A detailed analysis further explores the conditions where premium fuel provides actual performance benefits versus when it is unnecessary.[27]
Octane rating is measured relative to a mixture of2,2,4-trimethylpentane (anisomer ofoctane) and n-heptane. There are different conventions for expressing octane ratings, so the same physical fuel may have several different octane ratings based on the measure used. One of the best known is the research octane number (RON).
The octane rating of typical commercially available gasoline varies by country. InFinland,Sweden, andNorway, 95 RON is the standard for regular unleaded gasoline and 98 RON is also available as a more expensive option.
In the United Kingdom, over 95 percent of gasoline sold has 95 RON and is marketed as Unleaded or Premium Unleaded. Super Unleaded, with 97/98 RON and branded high-performance fuels (e.g., Shell V-Power, BP Ultimate) with 99 RON make up the balance. Gasoline with 102 RON may rarely be available for racing purposes.[28][29][30]
In the U.S., octane ratings in unleaded fuels vary between 85[31] and 87 AKI (91–92 RON) for regular, 89–90 AKI (94–95 RON) for mid-grade (equivalent to European regular), up to 90–94 AKI (95–99 RON) for premium (European premium).
91
92
93
94
95
96
97
98
99
100
101
102
Scandinavian
Regular
Premium
UK
Regular
Premium
Super
High-performance
USA
Regular
Mid-grade
Premium
As South Africa's largest city,Johannesburg, is located on theHighveld at 1,753 meters (5,751 ft) above sea level, theAutomobile Association of South Africa recommends 95-octane gasoline at low altitude and 93-octane for use in Johannesburg because "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".[32]
Octane rating became important as the military sought higher output foraircraft engines in the late 1920s and the 1940s. A higher octane rating allows a highercompression ratio orsupercharger boost, and thus higher temperatures and pressures, which translate to higher power output. Some scientists[who?] even predicted that a nation with a good supply of high-octane gasoline would have the advantage in air power. In 1943, theRolls-Royce Merlin aero engine produced 980 kilowatts (1,320 hp) using 100 RON fuel from a modest 27 liters (1,600 cu in) displacement. By the time ofOperation Overlord, both the RAF and USAAF were conducting some operations in Europe using 150 RON fuel (100/150avgas), obtained by adding 2.5 percentaniline to 100-octane avgas.[33] By this time, the Rolls-Royce Merlin 66 was developing 1,500 kilowatts (2,000 hp) using this fuel.
Gasoline, when used in high-compression internal combustion engines, tends to auto-ignite or "detonate" causing damagingengine knocking (also called "pinging" or "pinking"). To address this problem,tetraethyl lead (TEL) was widely adopted as an additive for gasoline in the 1920s. With a growing awareness of the seriousness of the extent of environmental and health damage caused by lead compounds, however, and the incompatibility of lead withcatalytic converters, governments began to mandate reductions in gasoline lead.
In the U.S., theEnvironmental Protection Agency issued regulations to reduce the lead content of leaded gasoline over a series of annual phases, scheduled to begin in 1973 but delayed by court appeals until 1976. By 1995, leaded fuel accounted for only 0.6 percent of total gasoline sales and under 1,800 metric tons (2,000 short tons; 1,800 long tons) of lead per year. From 1 January 1996, theU.S. Clean Air Act banned the sale of leaded fuel for use in on-road vehicles in the U.S. The use of TEL also necessitated other additives, such asdibromoethane.
European countries began replacing lead-containing additives by the end of the 1980s, and by the end of the 1990s, leaded gasoline was banned within the entire European Union with an exception forAvgas 100LL forgeneral aviation.[34] The UAE started to switch to unleaded in the early 2000s.[35]
Reduction in the average lead content of human blood may be a major cause for falling violent crime rates around the world[36] including South Africa.[37] A study found a correlation between leaded gasoline usage and violent crime (seeLead–crime hypothesis).[38][39] Other studies found no correlation.
In August 2021, theUN Environment Programme announced that leaded petrol had been eradicated worldwide, withAlgeria being the last country to deplete its reserves.UN Secretary-GeneralAntónio Guterres called the eradication of leaded petrol an "international success story". He also added: "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 called the announcement "the end of one toxic era".[40] However, leaded gasoline continues to be used in aeronautic, auto racing, and off-road applications.[41] The use of leaded additives is still permitted worldwide for the formulation of some grades ofaviation gasoline such as100LL, because the required octane rating is difficult to reach without the use of leaded additives.
Lead replacement petrol (LRP) was developed for vehicles designed to run on leaded fuels and incompatible with unleaded fuels. Rather than tetraethyllead, it contains other metals such aspotassium compounds ormethylcyclopentadienyl manganese tricarbonyl (MMT); these are purported to buffer soft exhaust valves and seats so that they do not suffer recession due to the use of unleaded fuel.
LRP was marketed during and after the phaseout of leaded motor fuels in the United Kingdom,Australia,South Africa, and some other countries.[vague] Consumer confusion led to a widespread mistaken preference for LRP rather than unleaded,[42] and LRP was phased out 8 to 10 years after the introduction of unleaded.[43]
Leaded gasoline was withdrawn from sale in Britain after 31 December 1999, seven years afterEEC regulations signaled the end of production for cars using leaded gasoline in member states. At this stage, a large percentage of cars from the 1980s and early 1990s which ran on leaded gasoline were still in use, along with cars that could run on unleaded fuel. However, the declining number of such cars on British roads saw many gasoline stations withdrawing LRP from sale by 2003.[44]
Methylcyclopentadienyl manganese tricarbonyl (MMT) is used in Canada and the U.S. to boost octane rating.[45] Its use in the U.S. has been restricted by regulations, although it is currently allowed.[46] Its use in the European Union is restricted by Article 8a of the Fuel Quality Directive[47] following its testing under the Protocol for the evaluation of effects of metallic fuel-additives on the emissions performance of vehicles.[48]
Fuel stabilizers (antioxidants and metal deactivators)
Substitutedphenols and derivatives ofphenylenediamine are common antioxidants used to inhibit gum formation in gasoline
Gummy, sticky resin deposits result fromoxidative degradation of gasoline during long-term storage. These harmful deposits arise from the oxidation ofalkenes and other minor components in gasoline[citation needed] (seedrying oils). Improvements in refinery techniques have generally reduced the susceptibility of gasolines to these problems. Previously, catalytically or thermally cracked gasolines were most susceptible to oxidation. The formation of gums is accelerated by copper salts, which can be neutralized by additives calledmetal deactivators.
This degradation can be prevented through the addition of 5–100 ppm ofantioxidants, such asphenylenediamines and otheramines.[11] Hydrocarbons with abromine number of 10 or above can be protected with the combination of unhindered or partially hinderedphenols and oil-soluble strong amine bases, such as hindered phenols. "Stale" gasoline can be detected by acolorimetricenzymatic test fororganic peroxides produced by oxidation of the gasoline.[49]
Gasolines are also treated withmetal deactivators, which are compounds that sequester (deactivate) metal salts that otherwise accelerate the formation of gummy residues. The metal impurities might arise from the engine itself or as contaminants in the fuel.
Gasoline, as delivered at the pump, also contains additives to reduce internal engine carbon buildups, improvecombustion and allow easier starting in cold climates. High levels of detergent can be found inTop Tier Detergent Gasolines. The specification for Top Tier Detergent Gasolines was developed by four automakers:GM,Honda,Toyota, andBMW. According to the bulletin, the minimal U.S.EPA requirement is not sufficient to keep engines clean.[50] Typical detergents includealkylamines andalkyl phosphates at a level of 50–100 ppm.[11]
In the EU, 5 percentethanol can be added within the common gasoline spec (EN 228). Discussions are ongoing to allow 10 percent blending of ethanol (available in Finnish, French and German gasoline stations). In Finland, most gasoline stations sell 95E10, which is 10 percent ethanol, and 98E5, which is 5 percent ethanol. Most gasoline sold in Sweden has 5–15 percent ethanol added. Three different ethanol blends are sold in the Netherlands—E5, E10 and hE15. The last of these differs from standard ethanol–gasoline blends in that it consists of 15 percenthydrous ethanol (i.e., the ethanol–waterazeotrope) instead of the anhydrous ethanol traditionally used for blending with gasoline.
Legislation requires retailers to label fuels containing ethanol on the dispenser, and limits ethanol use to 10 percent of gasoline in Australia. Such gasoline is commonly calledE10 by major brands, and it is cheaper than regular unleaded gasoline.
The federalRenewable Fuel Standard (RFS) effectively requires refiners and blenders to blend renewablebiofuels (mostly ethanol) with gasoline, sufficient to meet a growing annual target of total gallons blended. Although the mandate does not require a specific percentage of ethanol, annual increases in the target combined with declininggasoline consumption have caused the typical ethanol content in gasoline to approach 10 percent. Most fuel pumps display a sticker that states that the fuel may contain up to 10 percent ethanol, an intentional disparity that reflects the varying actual percentage. In parts of the U.S., ethanol is sometimes added to gasoline without an indication that it is a component.
In October 2007, theGovernment of India decided to make five percent ethanol blending (with gasoline) mandatory. Currently, 10 percent ethanol blended product (E10) is being sold in various parts of the country.[52][53] Ethanol has been found in at least one study to damage catalytic converters.[54]
Though gasoline is a naturally colorless liquid, many gasolines are dyed in various colors to indicate their composition and acceptable uses. In Australia, the lowest grade of gasoline (RON 91) was dyed a light shade of red/orange, but is now the same color as the medium grade (RON 95) and high octane (RON 98), which are dyed yellow.[55] In the U.S., aviation gasoline (avgas) is dyed to identify its octane rating and to distinguish it from kerosene-based jet fuel, which is left colorless.[56] In Canada, the gasoline for marine and farm use is dyed red and is not subject to fuel excise tax in most provinces.[57]
Oxygenate blending addsoxygen-bearing compounds such asmethanol,MTBE,ETBE,TAME,TAEE,ethanol, andbiobutanol. The presence of these oxygenates reduces the amount ofcarbon monoxide and unburned fuel in the exhaust. In many areas throughout the U.S., oxygenate blending is mandated by EPA regulations to reduce smog and other airborne pollutants. For example, in Southern California fuel must contain two percent oxygen by weight, resulting in a mixture of 5.6 percent ethanol in gasoline. The resulting fuel is often known as reformulated gasoline (RFG) or oxygenated gasoline, or, in the case of California, California reformulated gasoline (CARBOB). The federal requirement that RFG contain oxygen was dropped on 6 May 2006 because the industry had developedVOC-controlled RFG that did not need additional oxygen.[58]
MTBE was phased out in the U.S. due to groundwater contamination and the resulting regulations and lawsuits. Ethanol and, to a lesser extent, ethanol-derived ETBE are common substitutes. A common ethanol-gasoline mix of 10 percent ethanol mixed with gasoline is calledgasohol or E10, and an ethanol-gasoline mix of 85 percent ethanol mixed with gasoline is calledE85. The most extensive use of ethanol takes place inBrazil, where the ethanol is derived fromsugarcane. In 2004, over 13 billion liters (3.4×10^9 U.S. gal) of ethanol was produced in the U.S. for fuel use, mostly fromcorn and sold as E10. E85 is slowly becoming available in much of the U.S., though many of the relatively few stations vending E85 are not open to the general public.[59]
The use ofbioethanol and bio-methanol, either directly or indirectly by conversion of ethanol to bio-ETBE, or methanol to bio-MTBE is encouraged by the European UnionDirective on the Promotion of the use of biofuels and other renewable fuels for transport. Since producing bioethanol from fermented sugars and starches involvesdistillation, though, ordinary people in much of Europe cannot legally ferment and distill their own bioethanol at present (unlike in the U.S., where getting aBATF distillation permit has been easy since the1973 oil crisis).
Thesafety data sheet for a 2003Texan unleaded gasoline shows at least 15 hazardous chemicals occurring in various amounts, includingbenzene (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),methyltert-butyl ether (MTBE) (up to 18 percent by volume, in some states), and about 10 others.[60] Hydrocarbons in gasoline generally exhibit low acute toxicities, withLD50 of 700–2700 mg/kg for simple aromatic compounds.[61] Benzene and many antiknocking additives arecarcinogenic.
People can be exposed to gasoline in the workplace by swallowing it, breathing in vapors, skin contact, and eye contact. Gasoline is toxic. TheNational Institute for Occupational Safety and Health (NIOSH) has also designated gasoline as a carcinogen.[62] Physical contact, ingestion, or inhalation can cause health problems. Since ingesting large amounts of gasoline can cause permanent damage to major organs, a call to a local poison control center or emergency room visit is indicated.[63]
Contrary tocommon misconception, swallowing gasoline does not generally require special emergency treatment, and inducing vomiting does not help, and can make it worse. 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'sAgency for Toxic Substances and Disease Registry says not to induce vomiting,lavage, or administeractivated charcoal.[64][65]
Inhaled (huffed) gasoline vapor is a common intoxicant. Users concentrate and inhale gasoline vapor in a manner not intended by the manufacturer to produceeuphoria andintoxication. Gasoline inhalation has become epidemic in some poorer communities and indigenous groups in Australia, Canada, New Zealand, and some Pacific Islands.[66] The practice is thought to cause severe organ damage, along with other effects such asintellectual disability and variouscancers.[67][68][69][70]
In Canada, Native children in the isolated Northern Labrador community ofDavis Inlet were the focus of national concern in 1993, when many were found to be sniffing gasoline. The Canadian and provincialNewfoundland and Labrador governments intervened on several occasions, sending many children away for treatment. Despite being moved to the new community ofNatuashish in 2002, serious inhalant abuse problems have continued. Similar problems were reported inSheshatshiu in 2000 and also inPikangikum First Nation.[71] In 2012, the issue once again made the news media in Canada.[72]
Australia has long faced a petrol (gasoline) sniffing problem in isolated and impoverishedaboriginal communities. Although some sources argue that sniffing was introduced by U.S.servicemen stationed in the nation'sTop End duringWorld War II[73] or through experimentation by 1940s-eraCobourg Peninsula sawmill workers,[74] other sources claim that inhalant abuse (such as glue inhalation) emerged in Australia in the late 1960s.[75] Chronic, heavy petrol sniffing appears to occur among remote, impoverishedindigenous communities, where the ready accessibility of petrol has helped to make it a common substance for abuse.
In Australia, petrol sniffing now occurs widely throughout remote Aboriginal communities in theNorthern Territory,Western Australia, northern parts ofSouth Australia, andQueensland.[76] The number of people sniffing petrol goes up and down over time as young people experiment or sniff occasionally. "Boss", or chronic, sniffers may move in and out of communities; they are often responsible for encouraging young people to take it up.[77] In 2005, theGovernment of Australia andBP Australia began the usage ofOpal fuel in remote areas prone to petrol sniffing.[78] Opal is a non-sniffable fuel (which is much less likely to cause a high) and has made a difference in some indigenous communities.
Uncontrolled burning of gasoline produces large quantities ofsoot andcarbon monoxide.
Gasoline is flammable with lowflash point of −23 °C (−9 °F). Gasoline has alower explosive limit of 1.4 percent by volume and anupper explosive limit of 7.6 percent. If the concentration is below 1.4 percent, the air-gasoline mixture is too lean and does not ignite. If the concentration is above 7.6 percent, the mixture is too rich and also does not ignite. However, gasoline vapor rapidly mixes and spreads with air, making unconstrained gasoline quickly flammable.
Theexhaust gas generated by burning gasoline is harmful to both the environment and to human health. After CO is inhaled into the human body, it readily combines with hemoglobin in the blood, and its affinity is 300 times that of oxygen. Therefore, the hemoglobin in the lungs combines with CO instead of oxygen, causing the human body to behypoxic, causing headaches, dizziness, vomiting, and other poisoning symptoms. In severe cases, it may lead to death.[79][80] Hydrocarbons only affect the human body when their concentration is quite high, and their toxicity level depends on the chemical composition. The hydrocarbons produced by incomplete combustion include alkanes, aromatics, and aldehydes. Among them, a concentration of methane and ethane over 35 g/m3 (0.035 oz/cu ft) will cause loss of consciousness or suffocation, a concentration of pentane and hexane over 45 g/m3 (0.045 oz/cu ft) will have an anesthetic effect, and aromatic hydrocarbons will have more serious effects on health, blood toxicity,neurotoxicity, and cancer. If the concentration of benzene exceeds 40 ppm, it can cause leukemia, and xylene can cause headache, dizziness, nausea, and vomiting. Human exposure to large amounts of aldehydes can cause eye irritation, nausea, and dizziness. In addition to carcinogenic effects, long-term exposure can cause damage to the skin, liver, kidneys, and cataracts.[81] After NOx enters the alveoli, it has a severe stimulating effect on the lung tissue. It can irritate the conjunctiva of the eyes, cause tearing, and cause pink eyes. It also has a stimulating effect on the nose, pharynx, throat, and other organs. It can cause acute wheezing, breathing difficulties, red eyes, sore throat, and dizziness causing poisoning.[81][82]Fine particulates are also dangerous to health.[83]
The air pollution in many large cities has changed from coal-burning pollution to "motor vehicle pollution". In the U.S., transportation is the largest source of carbon emissions, accounting for 30 percent of the total carbon footprint of the U.S.[84] Combustion of gasoline produces 2.35 kilograms per liter (19.6 lb/U.S. gal) of carbon dioxide, agreenhouse gas.[85][86]
Unburnt gasoline andevaporation from the tank, when in theatmosphere, react insunlight to producephotochemical smog. Vapor pressure initially rises with some addition of ethanol to gasoline, but the increase is greatest at 10 percent by volume.[87] At higher concentrations of ethanol above 10 percent, the vapor pressure of the blend starts to decrease. At a 10 percent ethanol by volume, the rise in vapor pressure may potentially increase the problem of photochemical smog. This rise in vapor pressure could be mitigated by increasing or decreasing the percentage of ethanol in the gasoline mixture. The chief risks of such leaks come not from vehicles, but gasoline delivery truck accidents and leaks from storage tanks. Because of this risk, most (underground) storage tanks now have extensive measures in place to detect and prevent any such leaks, such as monitoring systems (Veeder-Root, Franklin Fueling).
Production of gasoline consumes 1.5 liters per kilometer (0.63 U.S. gal/mi) ofwater by driven distance.[88]
Gasoline use causes a variety of deleterious effects to the human population and to the climate generally. The harms imposed include a higher rate of premature death and ailments, such asasthma, caused byair pollution, higher healthcare costs for the public generally, decreasedcrop yields, missed work and school days due to illness, increasedflooding and otherextreme weather events linked toglobal climate change, and other social costs. The costs imposed on society and the planet are estimated to be $3.80 per gallon of gasoline, in addition to the price paid at the pump by the user. The damage to the health and climate caused by a gasoline-powered vehicle greatly exceeds that caused by electric vehicles.[89][90]
Gasoline can be released into the Earth's environment as an uncombusted liquid fuel, as a flammable liquid, or as a vapor by way of leakages occurring during its production, handling, transport and delivery.[91] Gasoline contains knowncarcinogens,[92][93][94] and gasolineexhaust is a health risk.[83] Gasoline is often used as a recreationalinhalant and can be harmful or fatal when used in such a manner.[95] When burned, one liter (0.26 U.S. gal) of gasoline emits about 2.3 kilograms (5.1 lb) ofCO2, agreenhouse gas, contributing tohuman-caused climate change.[96][97] Oil products, including gasoline, were responsible for about 32% of CO2 emissions worldwide in 2021.[98]
About 2.353 kilograms per liter (19.64 lb/U.S. gal) ofcarbon dioxide (CO2) are produced from burning gasoline that does not contain ethanol.[86] Most of the retail gasoline now sold in the U.S. contains about 10 percent fuel ethanol (or E10) by volume.[86] Burning E10 produces about 2.119 kilograms per liter (17.68 lb/U.S. gal) of CO2 that is emitted from the fossil fuel content. If the CO2 emissions from ethanol combustion are considered, then about 2.271 kilograms per liter (18.95 lb/U.S. gal) of CO2 are produced when E10 is combusted.[86]
Worldwide 7 liters of gasoline are burnt for every 100 km driven bycars and vans.[99]
In 2021, theInternational Energy Agency stated, "To ensure fuel economy and CO2 emissions standards are effective, governments must continue regulatory efforts to monitor and reduce the gap between real-world fuel economy and rated performance."[99]
Gasoline enters the environment through the soil, groundwater, surface water, and air. Therefore, humans may be exposed to gasoline through methods such as breathing, eating, and skin contact. For example, using gasoline-filled equipment, such as lawnmowers, drinking gasoline-contaminated water close to gasoline spills or leaks to the soil, working at a gasoline station, inhaling gasoline volatile gas when refueling at a gasoline station is the easiest way to be exposed to gasoline.[100]
TheInternational Energy Agency said in 2021 that "road fuels should be taxed at a rate that reflects their impact on people's health and the climate".[99]
Countries in Europe impose substantially highertaxes on fuels such as gasoline when compared to the U.S. The price of gasoline in Europe is typically higher than that in the U.S. due to this difference.[101]
From 1998 to 2004, the price of gasoline fluctuated between $0.26 and $0.53 per liter ($1 and $2/U.S. gal).[102] After 2004, the price increased until the average gasoline price reached a high of $1.09 per liter ($4.11/U.S. gal) in mid-2008 but receded to approximately $0.69 per liter ($2.60/U.S. gal) by September 2009.[102] The U.S. experienced an upswing in gasoline prices through 2011,[103] and, by 1 March 2012, the national average was $0.99 per liter ($3.74/U.S. gal). California prices are higher because the California government mandates unique California gasoline formulas and taxes.[104]
In the U.S., most consumer goods bear pre-tax prices, but gasoline prices are posted with taxes included. Taxes are added by federal, state, and local governments. As of 2009[update], the federal tax was $0.049 per liter ($0.184/U.S. gal) for gasoline and $0.064 per liter ($0.244/U.S. gal) fordiesel (excludingred diesel).[105]
About nine percent of all gasoline sold in the U.S. in May 2009 was premium grade, according to the Energy Information Administration.Consumer Reports magazine says, "If [your owner's manual] says to use regular fuel, do so—there's no advantage to a higher grade."[106] TheAssociated Press said premium gas—which has a higher octane rating and costs more per gallon than regular unleaded—should be used only if the manufacturer says it is "required".[107] Cars withturbocharged engines and high compression ratios often specify premium gasoline because higher octane fuels reduce the incidence of "knock", or fuel pre-detonation.[108] The price of gasoline varies considerably between the summer and winter months.[109]
There is a considerable difference between summer oil and winter oil in gasoline vapor pressure (Reid Vapor Pressure, RVP), which is a measure of how easily the fuel evaporates at a given temperature. The higher the gasoline volatility (the higher the RVP), the easier it is to evaporate. The conversion between the two fuels occurs twice a year, once in autumn (winter mix) and the other in spring (summer mix). The winter blended fuel has a higher RVP because the fuel must be able to evaporate at a low temperature for the engine to run normally. If the RVP is too low on a cold day, the vehicle will be difficult to start; however, the summer blended gasoline has a lower RVP. It prevents excessive evaporation when the outdoor temperature rises, reduces ozone emissions, and reduces smog levels. At the same time, vapor lock is less likely to occur in hot weather.[110]
Chevron published a free high-quality technical guideMotor Gasolines Technical Review using common language that explains gasoline production, blending, and combustion in an engine. The report covers the US and other locations globally.
^"Gasoline—a petroleum product".U.S. Energy Information Administration website. U.S. Energy Information Administration. 12 August 2016.Archived from the original on 24 May 2017. Retrieved15 May 2017.
^abcdWerner Dabelstein, Arno Reglitzky, Andrea Schütze and Klaus Reders "Automotive Fuels" inUllmann's Encyclopedia of Industrial Chemistry 2007, Wiley-VCH, Weinheim.doi:10.1002/14356007.a16_719.pub2
^Pradelle, Florian; Braga, Sergio L.; Martins, Ana Rosa F. A.; Turkovics, Franck; Pradelle, Renata N. C. (3 November 2015). "Gum Formation in Gasoline and Its Blends: A Review".Energy & Fuels.29 (12):7753–7770.doi:10.1021/acs.energyfuels.5b01894.
^Reyes, J. W. (2007)."The Impact of Childhood Lead Exposure on Crime"(PDF).National Bureau of Economic Research. "a" ref citing Pirkle, Brody, et al. (1994).Archived(PDF) from the original on 17 January 2024. Retrieved26 May 2024.
^V. F. Andersen; J. E. Anderson; T. J. Wallington; S. A. Mueller; O. J. Nielsen (21 May 2010). "Vapor Pressures of Alcohol−Gasoline Blends".Energy Fuels.24 (6):3647–3654.doi:10.1021/ef100254w.
^Mehlman, MA (1990). "Dangerous properties of petroleum-refining products: carcinogenicity of motor fuels (gasoline)".Teratogenesis, Carcinogenesis, and Mutagenesis.10 (5):399–408.doi:10.1002/tcm.1770100505.ISSN2472-1727.PMID1981951.
^Baumbach, JI; Sielemann, S; Xie, Z; Schmidt, H (15 March 2003). "Detection of the gasoline components methyl tert-butyl ether, benzene, toluene, and m-xylene using ion mobility spectrometers with a radioactive and UV ionization source".Analytical Chemistry.75 (6):1483–90.doi:10.1021/ac020342i.PMID12659213.
^"Gasoline Sniffing".HealthyChildren.org. 28 December 2012.Archived from the original on 11 March 2024. Retrieved11 March 2024.
^Eyidogan, Muharrem; Ozsezen, Ahmet Necati; Canakci, Mustafa; Turkcan, Ali (2010). "Impact of alcohol–gasoline fuel blends on the performance and combustion characteristics of an SI engine".Fuel.89 (10): 2713.Bibcode:2010Fuel...89.2713E.doi:10.1016/j.fuel.2010.01.032.
.svg)
