Gasoline , or petrol , is a transparent, fractional distillation of petroleum, enhanced with a variety of additives; a 42 gallon barrel of crude oil yields about 19 gallons of gasoline, when processed in an oil refinery.
The 'anti-knock' characteristic of a particular gasoline blend, when used as a fuel in internal combustion engines, is measured by its octane rating. Gasoline is produced in several grades of octane rating. Tetraethyl lead, and other lead compounds are no longer used in most areas to regulate and increase octane-rating, but many other additives are put into gasoline to improve its chemical stability, control corrosiveness and provide fuel system 'cleaning,' and determine performance characteristics under intended use. Sometimes, gasoline also contains ethanol as an alternative fuel, for economic or environmental reasons.
Gasoline, as used worldwide in the vast number of internal combustion engines used in transport and industry, has a significant impact on the environment, both in local effects (e.g., smog) and in global effects (e.g., effect on the climate). Gasoline may also enter the environment uncombusted, as liquid and as vapors, from leakage and handling during production, transport and delivery, from storage tanks, from spills, etc. As an example of efforts to control such leakage, many (underground) storage tanks are required to have extensive measures in place to detect and prevent such leaks. The material safety data sheet for unleaded gasoline shows at least 15 hazardous chemicals occurring in various amounts. Benzene and many anti-knocking additives are carcinogenic.
Inhaled (huffed) gasoline vapor is a common intoxicant that has become epidemic in some poorer communities and indigenous groups in Australia, Canada, New Zealand, and some Pacific Islands. In response, Opal fuel has been developed by the BP Kwinana Refinery in Australia, and contains only 5% aromatics (unlike the usual 25%), which weakens the effects of inhalation.
- Octane rating 1
- Stability 2
- Energy content 3
- Density 4
- Chemical analysis and production 5
Antiknock additives 6.1
- Tetraethyllead 6.1.1
- MMT 6.1.2
- Fuel stabilizers (antioxidants and metal deactivators) 6.2
- Detergents 6.3
- European Union 6.4.1
- Brazil 6.4.2
- Australia 6.4.3
- United States of America 6.4.4
- India 6.4.5
- Dye 6.5
- Oxygenate blending 6.6
- Antiknock additives 6.1
- Environmental considerations 7.1
- Toxicity 7.2
- Inhalation 7.3
- Flammability 7.4
Use and pricing 8
- Europe 8.1
- United States 8.2
- History 9
- Etymology and terminology 10
- Comparison with other fuels 11
- See also 12
- Notes 13.1
- Bibliography 13.2
- External links 14
Spark ignition engines are designed to burn gasoline in a controlled process called deflagration. In some cases, however, the unburned mixture can autoignite by detonating from pressure and heat alone, rather than ignite from the spark plug at exactly the right time, which causes rapid pressure rise which can damage the engine. This phenomenon is often referred to as engine knocking or end-gas knock. One way to reduce knock in spark ignition engines is to increase the gasoline's resistance to autoignition, which is expressed by its octane rating.
Octane rating is measured relative to a mixture of 2,2,4-trimethylpentane (an isomer of octane) and n-heptane. There are different conventions for expressing octane ratings, so a fuel may have several different octane ratings based on the measure used. Research octane number (RON) for commercially-available gasoline varies by country. In Finland, Sweden, and Norway, 95 RON is the standard for regular unleaded gasoline and 98 RON is also available as a more expensive option. In the UK, ordinary regular unleaded gasoline is 95 RON (commonly available), premium unleaded gasoline is always 97 RON, and super unleaded is usually 97-98 RON. However, both Shell and BP produce fuel at 102 RON for cars with high-performance engines, and the supermarket chain Tesco began in 2006 to sell super unleaded gasoline rated at 99 RON. In the US, octane ratings in unleaded fuels can vary between 85 and 87 AKI (91-92 RON) for regular, through 89-90 AKI (94-95 RON) for mid-grade (European regular), up to 90-94 AKI (95-99 RON) for premium (European premium).
South Africa's largest city is Johannesburg is located on the Highveld at 1,753 metres (5,751 ft) above sea-level. So the South African AA recommends 95 octane petrol (gasoline) as 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".
The octane rating became important as the military sought higher output for aircraft engines in the late 1930s and the 1940s. A higher octane rating allows a higher compression ratio or supercharger boost, and thus higher temperatures and pressures, which translate to higher power output. Some scientists even predicted that a nation with a good supply of high octane gasoline would have the advantage in air power. In 1943, the Rolls Royce Merlin aero engine produced 1,320 horsepower (984 kW) using 100 RON fuel from a modest 27 liter displacement. Towards the end of the second world war, experiments were conducted using 150 RON fuel (100/150 avgas), obtained by adding 2.5% aniline to 100 octane avgas.
Quality gasoline should be stable almost indefinitely if stored properly. Such storage should be in an airtight container (to prevent oxidation or water vapors mixing) that can withstand the vapor 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 be created, which can corrode system components and accumulate on wetted 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).
The presence of these degradation products in fuel tank, lines, carburetor or fuel injection components makes it harder to start the engine, or causes reduced engine performance. On resumption of regular engine use, the buildup is often 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. Some typical fuel stabilizers are proprietary mixtures containing mineral spirits, isopropyl alcohol, 1,2,4-trimethylbenzene,or other additives. Fuel stabilizer is commonly used for small engines, such as lawnmower and tractor engines, especially when their use is seasonal (low 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.
- 2 C8H18 + 25 O2 → 16 CO2 + 18 H2O
Gasoline contains about 42.4 MJ/kg (120 MJ/US gal, 33.3 kWh/US gal) quoting the lower heating value . Gasoline blends differ, and therefore actual energy content varies according to the season and producer by up to 4% more or less than the average, according to the US EPA. On average, about 74 L of gasoline (19.5 US gal, 16.3 imp gal) are available from a barrel of crude oil (about 46% by volume), varying due to quality of crude and grade of gasoline. The remainder are products ranging from tar to naphtha.
A high-octane-rated fuel, such as liquefied petroleum gas (LPG) has an overall lower power output at the typical 10:1 compression ratio of a gasoline engine. However, with an engine tuned to the use of LPG (i.e. via higher compression ratios, such as 12:1 instead of 10:1), this lower power output can be eliminated. This is because higher-octane fuels allow for a higher compression ratio without knocking, resulting in a higher cylinder temperature, which improves efficiency. 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. An Atkinson 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 of diesel engines, along with the elimination of pumping losses due to throttling of the intake air flow.
The lower energy content (per liter) of LPG in comparison to gasoline is due mainly to its lower Standard enthalpy of formation).
The density of gasoline ranges from 0.71–0.77 kg/L (719.7 kg/m3 ; 0.026 lb/in3; 6.073 lb/US gal; 7.29 lb/imp gal), higher densities having a greater volume of aromatics. Since gasoline floats on water, water cannot generally be used to extinguish a gasoline fire unless used in a fine mist. Finished marketable gasoline is traded with a standard reference of 0.755 kg/L, and its price is escalated/de-escalated according to its actual density.
Chemical analysis and production
Gasoline is produced in oil refineries. Roughly 19 gallons of gasoline is derived from a 42 gallon barrel of crude oil. Material separated from crude oil via distillation, called virgin or straight-run gasoline, does not meet specifications for modern engines (particularly the octane rating, see below), but can be pooled to the gasoline blend.
The various refinery streams blended to make gasoline have different characteristics. Some important streams are:
- straight-run gasoline, usually also called naphtha is distilled directly from crude oil. Once the leading source of fuel, its low octane rating required lead additives. It is low in aromatics (depending on the grade of crude oil), containing some cycloalkanes (naphthenes) and no olefins. Between 0 and 20% of this stream is pooled into the finished gasoline, because the supply of this fraction is insufficient and its RON is too low.. The chemical properties (namely octane and RVP) of the straight-run gasoline can be improved through reforming and isomerisation. However, before feeding those units, the naphtha needs to be split in light and heavy naphtha. Straight-run gasoline can be also used as a feedstock into steam-crackers to produce olefins.
- reformate, produced in a catalytic reformer has a high octane rating with high aromatic content, and relatively low olefins (alkenes). Most of the benzene, toluene, and xylene (the so-called BTX) are more valuable as chemical feedstocks and are thus removed to some extent.
- catalytic cracked gasoline or catalityc cracked naphtha, produced from a catalytic cracker, with a moderate octane rating, high olefins (alkene) content, and moderate aromatics level.
- hydrocrackate (heavy, mid, and light) produced from a hydrocracker, with medium to low octane rating and moderate aromatic levels.
- alkylate is produced in an alkylation unit, using as feedstocks isobutane and alkenes. Alkylate contains nil aromatics and olefins and has high MON.
- isomerate is obtained by isomerizing low octane straight run gasoline to iso-parafins (like isooctane). Isomerate has medium RON and MON, but nil aromatics and olefins.
The terms above are the jargon used in the oil industry and terminology varies.
Overall, a typical gasoline is predominantly a mixture of paraffins (alkanes), cycloalkanes (naphthenes), and olefins (alkenes). The actual ratio depends on:
- the oil refinery that makes the gasoline, as not all refineries have the same set of processing units;
- crude oil feed used by the refinery;
- the grade of gasoline, in particular, the octane rating.
Currently, many countries set limits on gasoline aromatics in general, benzene in particular, and olefin (alkene) content. Such regulations led to increasing preference for high octane pure paraffin (alkane) components, such as alkylate, and is forcing refineries to add processing units to reduce benzene content. In the EU the benzene limit is set at 1% volume for all grade of automotive gasoline.
Gasoline can also contain other organosulfur compounds, but these are usually removed at the refinery.
Almost all countries in the world have phased out automotive leaded fuel. In 2011 six countries in the world were still using leaded gasoline: Afghanistan, Myanmar, North Korea, Algeria, Iraq and Yemen. It was expected that by the end of 2013 those countries would ban leaded petrol, but actually it will take longer. Algeria will replace leaded with unleaded automotive fuel only in 2015. Different additives have replaced the lead compounds. The most popular additives include aromatic hydrocarbons, ethers and alcohol (usually ethanol or methanol). For technical reasons the use of leaded additives is still permitted world-wide for the formulation of some grades of aviation gasoline such as 100LL, because the required octane rating would be technically infeasible to reach without the use of leaded additives.
Gasoline, when used in high-compression internal combustion engines, tends to autoignite (detonate) causing damaging "engine knocking" (also called "pinging" or "pinking") noise. To address this problem, tetraethyllead (TEL) was widely adopted as an additive for gasoline in the 1920s. With the discovery of the extent of environmental and health damage caused by the lead, however, and the incompatibility of lead with catalytic converters, leaded gasoline was phased out beginning in 1973. By 1995, leaded fuel accounted for only 0.6% of total gasoline sales and less than 2000 short tons (1814 t) of lead per year in the USA. From 1 January 1996, the U.S. Clean Air Act banned the sale of leaded fuel for use in on-road vehicles in the USA. The use of TEL also necessitated other additives, such as dibromoethane. First European countries started replacing lead by the end of the 80's and by the end of the 90's leaded petrol was banned within the entire European Union.
Methylcyclopentadienyl manganese tricarbonyl (MMT) is used in Canada and in Australia to boost octane. It also helps old cars designed for leaded fuel run on unleaded fuel without need for additives to prevent valve problems. Its use in the US has been restricted by regulations.
Fuel stabilizers (antioxidants and metal deactivators)
Gummy, sticky resin deposits result from oxidative degradation of gasoline upon long term storage. These harmful deposits arise from the oxidation of alkenes and other minor components in gasoline (see drying oils). Improvements in refinery techniques have generally reduced the susceptibility of gasolines to these problems. Previously, catalytically or thermally cracked gasolines are most susceptible to oxidation. The formation of these gums is accelerated by copper salts, which can be neutralized by additives called metal deactivators.
This degradation can be prevented through the addition of 5–100 ppm of
- Down the Gasoline Trail Handy Jam Organization, 1935 (Cartoon)
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- MMT-US EPA
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- What's the difference between premium and regular gas? (from The Straight Dope)
- "Here Comes Winter Gasoline" R-Squared Energy Blog 14 September 2006
- International Fuel Prices 2005 with diesel and gasoline prices of 172 countries
- EIA — Gasoline and Diesel Fuel Update
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- Durability of various plastics: Alcohols vs. Gasoline
- Dismissal of the Claims of a Biological Connection for Natural petroleum.
- Fuel Economy Impact Analysis of RFG i.e. reformulated gasoline. Has lower heating value data, actual energy content is higher see higher heating value
- gasoline Sniffing Fact File Sheree Cairney, www.abc.net.au, Published 24th November 2005. Retrieved 13th October 2007, a modified version of the original article, now archived 
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- , April 1935Popular Mechanics"Best Gasoline Will Win War of the Future" article at bottom of page 524
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- Bioenergy Feedstock Development Programs at Oak Rodge National Laboratory
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- Aviation fuel
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- Diesel fuel
- Filling station
- Fuel dispenser
- Gasoline and diesel usage and pricing
- Gasoline gallon equivalent
- Internal combustion engine (ICE)
- List of automotive fuel brands
- Natural-gas condensate#Drip gas
- Octane rating
- Oil price increases since 2003
(*) Diesel fuel is not used in a gasoline engine, so its low octane rating is not an issue; the relevant metric for diesel engines is the cetane number
|Fuel type||Gross MJ/L||MJ/kg||
|Net BTU/gal (U.S.)||RON|
|Autogas (LPG) (Consisting mostly of C2 to C4 range hydrocarbons)||26.8||46||5,587||6,710||108|
|Avgas (high octane gasoline)||33.5||46.8||144,400||120,200||112,000|
|Jet fuel (kerosene based)||35.1||43.8||151,242||125,935|
|Jet fuel (naphtha)||127,500||118,700|
|Liquefied natural gas||25.3||~55||109,000||90,800|
|Liquefied petroleum gas||91,300||83,500|
|Hydrogen||10.1 (at 20 kelvin)||142||130|
Comparison with other fuels
In many countries, gasoline has a colloquial name derived from that of the chemical benzene (e.g., German Benzin, Dutch benzine, Italian benzina, Polish benzyna, Chile bencina, Thai เบนซิน bayn sin , Greek βενζίνη venzini, Romanian benzină, Swedish bensin, Arabic بنزين binzīn). Argentina, Uruguay and Paraguay use the colloquial name nafta derived from that of the chemical naphtha.
Variant spellings of "gasoline" have been used to refer to raw petroleum since the 16th century. "Petrol" was first used as the name of a refined petroleum product around 1870 by British wholesaler Carless, Capel & Leonard, who marketed it as a solvent. When the product later found a new use as a motor fuel, Frederick Simms, an associate of Gottlieb Daimler, suggested to Carless that they register the trade mark "petrol", but by this time the word was already in general use, possibly inspired by the French pétrole, and the registration was not allowed. Carless registered a number of alternative names for the product, while their competitors used the term "motor spirit" until the 1930s.
"Gasoline" is cited (under the spelling "gasolene") from 1863 in the Oxford English Dictionary. It was never a trademark, although it may have been derived from older trademarks such as "Cazeline" and "Gazeline".
Etymology and terminology
The first automotive combustion engines, so-called Otto engines, were developed in the last quarter of the 19th century in Germany. The fuel was a relatively volatile hydrocarbon obtained from coal gas. With a boiling point near 85 °C (octanes boil about 40 °C higher), it was well suited for early carburetors (evaporators). The development of a "spray nozzle" carburetor enabled the use of less volatile fuels. Further improvements in engine efficiency were attempted at higher compression ratios, but early attempts were blocked by knocking (premature explosion of fuel). In the 1920s, antiknock compounds were introduced by Migley and Boyd, specifically tetraethyllead (TEL). This innovation started a cycle of improvements in fuel efficiency that coincided with the large-scale development of oil refining to provide more products in the boiling range of gasolines. In the 1950s oil refineries started to focus on high octane fuels, and then detergents were added to gasoline to clean the jets and carburetors. The 1970s witnessed greater attention to the environmental consequences of burning gasoline. These considerations led to the phasing out of TEL and its replacement by other antiknock compounds. Subsequently, low-sulfur gasoline was introduced, in part to preserve the catalysts in modern exhaust systems.
About 9% of all gasoline sold in the US 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.” The Associated Press said premium gas—which is a higher octane and costs more per gallon than regular unleaded—should be used only if the manufacturer says it is “required”. Cars with turbocharged engines and high compression ratios often specify premium gas because higher octane fuels reduce the incidence of "knock", or fuel pre-detonation. If regular fuel is used, the engine computer usually switches to a less aggressive fuel map to protect the engine, and performance is decreased.
In the United States, 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, the federal tax is 18.4¢ per gallon for gasoline and 24.4¢ per gallon for diesel (excluding  However, many states' taxes are a percentage and thus vary in amount depending on the cost of the gasoline.
From 1998 to 2004, the price of gasoline fluctuated between $1 and $2  and by 1 March 2012, the national average was $3.74 per gallon.
Unlike the US, countries in Europe impose substantial taxes on fuels such as gasoline. The price of gasoline in Europe is typically more than twice that in the US.
The United States accounts for about 44% of the world’s gasoline consumption. In 2003 The US consumed 476 gigaliters (126 billion U.S. gallons; 105 billion imperial gallons), which equates to 1.3 gigaliters (340 million U.S. gallons; 290 million imperial gallons) of gasoline each day. The US used about 510 gigaliters (130 billion U.S. gallons; 110 billion imperial gallons) of gasoline in 2006, of which 5.6% was mid-grade and 9.5% was premium grade.
Use and pricing
Like other alkanes, gasoline burns in a limited range of its vapor phase and, coupled with its volatility, this makes leaks highly dangerous when sources of ignition are present. Gasoline has a lower explosion limit of 1.4% by volume and an upper explosion limit of 7.6%. If the concentration is below 1.4%, the air-gasoline mixture is too lean and does not ignite. If the concentration is above 7.6%, the mixture is too rich and also does not ignite. However, gasoline vapor rapidly mixes and spreads with air, making unconstrained gasoline quickly flammable.
Huffed gasoline is a common intoxicant that has become epidemic in some poorer communities and indigenous groups in Australia, Canada, New Zealand, and some Pacific Islands. In response, Opal fuel has been developed by the BP Kwinana Refinery in Australia, and contains only 5% aromatics (unlike the usual 25%), which weakens the effects of inhalation.
The material safety data sheet for unleaded gasoline shows at least 15 hazardous chemicals occurring in various amounts, including benzene (up to 5% by volume), toluene (up to 35% by volume), naphthalene (up to 1% by volume), trimethylbenzene (up to 7% by volume), methyl tert-butyl ether (MTBE) (up to 18% by volume, in some states) and about ten others. Hydrocarbons in gasoline generally exhibit low acute toxicities, with LD50 of 700 – 2700 mg/kg for simple aromatic compounds. Benzene and many antiknocking additives are carcinogenic.
The chief risks of such leaks come not from vehicles, but from 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).
The main concern with gasoline on the environment, aside from the complications of its extraction and refining, is the potential effect on the climate. Unburnt gasoline and evaporation from the tank, when in the atmosphere, react in sunlight to produce photochemical smog. Vapor pressure initially rises with some addition of ethanol to gasoline, but the increase is greatest at 10% by volume. At higher concentrations of ethanol above 10%, the vapor pressure of the blend starts to decrease. At a 10% 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 the percentage of ethanol in the gasoline mixture.
Combustion of 1 US gallon (3.8 L) of gasoline produces 8,788 grams (19.374 lb) of carbon dioxide (2.3 kg/l), a greenhouse gas.
MTBE use is being phased out in some states due to issues with contamination of ground water. In some places, such as California, it is already banned. Ethanol and, to a lesser extent, the ethanol-derived ETBE are common replacements. A common ethanol-gasoline mix of 10% ethanol mixed with gasoline is called gasohol or E10, and an ethanol-gasoline mix of 85% ethanol mixed with gasoline is called E85. The most extensive use of ethanol takes place in Brazil, where the ethanol is derived from sugarcane. In 2004, over 3.4 billion US gallons (2.8 billion imp gal/13 million m³) of ethanol was produced in the United States for fuel use, mostly from corn, and E85 is slowly becoming available in much of the United States, though many of the relatively few stations vending E85 are not open to the general public. The use of bioethanol, either directly or indirectly by conversion of such ethanol to bio-ETBE, is encouraged by the European Union Directive on the Promotion of the use of biofuels and other renewable fuels for transport. Since producing bioethanol from fermented sugars and starches involves distillation, though, ordinary people in much of Europe cannot legally ferment and distill their own bioethanol at present (unlike in the US, where getting a BATF distillation permit has been easy since the 1973 oil crisis).
VOC-controlled RFG that did not need additional oxygen.
In Canada the gasoline for marine and farm use is dyed red and is not subject to road tax .
In the United States, aviation gasoline (avgas) is dyed to identify its octane rating and to distinguish it from kerosene-based jet fuel, which is clear.
In Australia, the lowest grade of petrol (RON 91) is dyed a light shade of red/orange and the medium grade (RON 95) is dyed yellow.
The Government of India in October 2007 decided to make 5% ethanol blending (with gasoline) mandatory. Currently, 10% Ethanol blended product (E10) is being sold in various parts of the country.
The federal Renewable Fuel Standard (RFS) effectively requires refiners and blenders to blend renewable biofuels (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 declining gasoline consumption has caused the typical ethanol content in gasoline to approach 10%. Most fuel pumps display a sticker that states that the fuel may contain up to 10% ethanol, an intentional disparity that reflects the varying actual percentage. Until late 2010, fuels retailers were only authorized to sell fuel containing up to 10 percent ethanol (E10), and most vehicle warranties (except for flexible fuel vehicles) authorize fuels that contain no more than 10 percent ethanol. In parts of the United States, ethanol is sometimes added to gasoline without an indication that it is a component.
United States of America
Legislation requires retailers to label fuels containing ethanol on the dispenser, and limits ethanol use to 10% of petrol in Australia. Such petrol is commonly called E10 by major brands, and it is cheaper than regular unleaded petrol.
In Brazil, the Brazilian National Agency of Petroleum, Natural Gas and Biofuels (ANP) requires gasoline for automobile use to have from 18 to 25% of ethanol added to its composition.
In the EU, 5% ethanol can be added within the common gasoline spec (EN 228). Discussions are ongoing to allow 10% blending of ethanol (available in Finnish, French and German gas stations). In Finland most gasoline stations sell 95E10, which is 10% of ethanol; and 98E5, which is 5% ethanol. Most gasoline sold in Sweden has 5-15% ethanol added.
Gasoline, as delivered at the pump, also contains additives to reduce internal engine carbon buildups, improve combustion, and to allow easier starting in cold climates. High levels of detergent can be found in Top Tier Detergent Gasolines. The specification for Top Tier Detergent gasolines was developed by four automakers: GM, Honda, Toyota and BMW. According to the bulletin, the minimal EPA requirement is not sufficient to keep engines clean. Typical detergents include alkylamines and alkyl phosphates at the level of 50-100 ppm.
Gasolines are also treated with metal 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.