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Gasoline (or '''petrol''') is a Petroleum -derived Liquid mixture consisting primarily of Hydrocarbon s, used as Fuel in Internal Combustion Engine s. Many Commonwealth Countries use the term petrol (abbreviated from ''petroleum spirit''). The term ''gasoline'' is commonly used in North America . The word is commonly shortened in Colloquial usage to " Gas " (see other meanings). The term ''mogas'', short for ''motor gasoline'', for use in cars is used to distinguish it from Avgas , ''aviation gasoline'' used in light Aircraft . This should be distinguished in usage from genuinely Gaseous fuels used in internal combustion engines such as Hydrogen . using the U.S. CPI ).]] Pharmaceutical Before Internal Combustion Engine s were invented in the mid-1800s, gasoline was sold in small bottles as a treatment against Lice and their eggs. At that time, the word "Petrol" was a Trade Name . This treatment method is no longer common because of the inherent fire hazard and the risk of Dermatitis . The word petrol may be derived from . Petrol is also abused as a psychoactive Inhalant . Etymology The word "gasolene" was coined in 1865 from the word Gas and the chemical suffix -ine/-ene. The modern spelling was first used in 1871. The shortened form "gas" was first recorded in American English in 1905. {Link without Title} Gasoline originally referred to any liquid used as the fuel for a gasoline-powered engine, other than diesel fuel or liquefied gas. Methanol racing fuel would have been classed as a type of gasoline. {Link without Title} The word "petrol" was first used in reference to the refined substance as early as 1892 (it previously referred to unrefined petroleum), and was registered as a trade name by English wholesaler Carless, Capel & Leonard. [http://www.chrysler-restorers-sa.org.au/crcmag154.pdf Bertha Benz got petrol for her famous drive from Mannheim to Pforzheim and back from chemists' shops. In Germany petrol is called ''Benzin,'' only the usage does not derive from her name but from the chemical Benzine . World War II and octane One interesting historical issue involving octane rating took place during WWII . Germany received nearly all its oil from Romania , and set up huge distilling plants in Germany to produce gasoline from Coal . In the US the oil was not "as good" and the oil industry had to invest heavily in various expensive boosting systems. This turned out to have benefits. The US industry started delivering fuels of ever-increasing Octane Rating s by adding more of the boosting agents and the infrastructure was in place for post war octane agents additive industry. Good crude oil was no longer a factor during wartime and by war's end, American aviation fuel was commonly 130 to 150 octane. This high octane could easily be used in existing engines to deliver much more power by increasing the pressure delivered by the Supercharger s. The Germans, relying entirely on "good" gasoline, had no such industry, and instead had to rely on ever-larger engines to deliver more power. However, German aviation engines were of the direct fuel injection type and could use methanol-water injection and Nitrous Oxide injection, which gave 50% more engine power for five minutes of dogfight. This could be done only five times or after 40 hours run-time and then the engine would have to be rebuilt. Most German aero engines used 87 octane fuel (called B4), while some high-powered engines used 100 octane (C2/C3) fuel. This historical "issue" is based on a very common misapprehension about wartime fuel octane numbers. There are two octane numbers for each fuel, one for lean mix and one for rich mix, rich being always greater. So, for example, a common British aviation fuel of the later part of the war was 100/125. The misapprehension that German fuels have a lower octane number (and thus a poorer quality) arises because the Germans quoted the lean mix octane number for their fuels while the Allies quoted the rich mix number for their fuels. Standard German high-grade aviation fuel used in the later part of the war (given the designation C3) had lean/rich octane numbers of 100/130. The Germans would list this as a 100 octane fuel while the Allies would list it as 130 octane. After the war the US Navy sent a Technical Mission to Germany to interview German petrochemists and examine German fuel quality. Their report entitled "Technical Report 145-45 Manufacture of Aviation Gasoline in Germany" chemically analyzed the different fuels and concluded that "Toward the end of the war the quality of fuel being used by the German fighter planes was quite similar to that being used by the Allies". CHEMICAL ANALYSIS AND PRODUCTION Gasoline is produced in Oil Refineries . Material that is separated from Crude Oil via Distillation , called natural gasoline, does not meet the required specifications for modern engines (in particular Octane Rating ; see below), but will form part of the blend. The bulk of a typical gasoline consists of Hydrocarbon s with between 5 and 12 Carbon Atom s per Molecule . The various refinery streams blended together to make gasoline all have different characteristics. Some important streams are:
(The terms used here are not always the correct chemical terms. Typically they are old fashioned, but they are the terms normally used in the oil industry. The exact terminology for these streams varies by oil company and by country.) Overall a typical gasoline is predominantly a mixture of paraffins ( Alkanes ), naphthenes ( Cycloalkane s), Aromatic s and olefins (alkenes). The exact ratios can depend on
Currently many countries set tight limits on gasoline Aromatic s in general, Benzene in particular, and olefins (alkene) content. This is increasing the demand for high octane pure paraffin (alkane) components, such as alkylate, and is forcing refineries to add processing units to reduce the benzene content. Gasoline can also contain some other s (deliberately added), plus small levels of contaminants, in particular Sulfur compounds such as Disulfides and Thiophene s. Some contaminants, in particular Thiol s and Hydrogen Sulfide , must be removed because they cause corrosion in engines. Volatility Gasoline is more volatile than the volatility limit changes every month and differs for each main distribution center, but most countries simply have a summer, winter and perhaps intermediate limit. In the United States, volatility is regulated in large urban centres to reduce the emission of unburned hydrocarbons. In large cities, so-called reformulated gasoline that is less prone to evaporation, among other properties, is required. Volatility standards may be relaxed (allowing more gasoline components into the atmosphere) during emergency anticipated gasoline shortages. For example, on and pollute the air, higher volatility gasoline (which contains less additives than gasoline whose volatility has been artificially lowered) effectively increases a nation's gasoline supply by making it easier for oil refiners to produce gasoline. Octane rating The most important characteristic of gasoline is its Octane Rating , which is a measure of how resistant gasoline is to premature detonation ( Knocking ). It is measured relative to a mixture of 2,2,4-trimethylpentane (an Isomer of Octane ) and n- Heptane . An 87-octane gasoline has the same Knock Resistance as a mixture of 87% isooctane and 13% n-heptane. The octane rating system was developed by the chemist Russell Marker . ENERGY CONTENT Gasoline contains about 45 Megajoule s per kilogram (MJ/kg) or 135MJ/US gallon. Volumetric Energy Density of some fuels compared to gasoline: A high octane fuel such as LPG has a lower energy content than lower octane gasoline, resulting in an overall lower power output at the regular compression ratio an engine ran at on gasoline. However, with an engine - this means less space in a cylinder on its combustion stroke, hence a higher cylinder temperature, less wasted hydrocarbons (therefore less pollution and wasted energy), and therefore higher power levels coupled with less pollution overall because of the greater efficiency. The main reason for the lower energy content (per litre) of LPG in comparison to gasoline is that it has a lower Density . Energy content per kilogram is higher than for gasoline (higher Hydrogen to Carbon ratio). Different countries have some variation in what RON (Research Octane Number) is standard for gasoline, or petrol. In the UK, ordinary regular unleaded petrol is 91 RON (not commonly available), premium unleaded petrol is always 95 RON, and super unleaded is usually 97-98 RON. In the US, octane ratings in fuels can vary between 86-87 AKI (91-92 RON) for regular, through 89-90 (94-95) for mid-grade (European Premium), up to 90-94 (RON 95-99) for premium unleaded or E10 (Super in Europe) ADDITIVES Lead The mixture known as gasoline, when used in high Compression internal combustion engines, has a tendency to ignite early (''pre-ignition'' or ''detonation'') causing a damaging " Engine Knocking " (also called "pinging") noise. Early research into this effect was led by A.H. Gibson and Harry Ricardo in England and Thomas Midgley and Thomas Boyd in the United States. The discovery that Lead additives modified this behavior led to the widespread adoption of the practice in the 1920s and therefore more powerful higher compression engines. The most popular additive was Tetra-ethyl Lead . However, with the recognition of the environmental and health damage caused by the lead, and the incompatibility of lead with Catalytic Converter s found on virtually all automobiles since 1975, this practice began to wane in the 1980s. Most countries are phasing out leaded fuel; different additives have replaced the lead compounds. The most popular additives include Aromatic Hydrocarbon s, Ether s and Alcohol (usually Ethanol or Methanol ). In the U.S., where lead was blended with gasoline, primarily to boost octane levels, since the early 1920s, standards to phase out leaded gasoline were first implemented in 1973. In 1995, leaded fuel accounted for only 0.6 % of total gasoline sales and less than 2,000 tons of lead per year. From January 1 , 1996 , the Clean Air Act banned the sale of leaded fuel for use in on-road vehicles. Possession and use of leaded petrol in a regular on-road vehicle now carries a maximum $10,000 fine in the United States. However, fuel containing lead may continue to be sold for off-road uses, including aircraft, racing cars, farm equipment, and marine engines until 2008. The ban on leaded gasoline was presumed to lower levels of lead in people's Blood stream and led to thousands of tons of lead being removed from the air. A side effect of the lead additives was protection of the Valve seats from erosion. Many Classic Car s' engines have needed modification to use lead-free fuels since leaded fuels became unavailable. 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. MMT Methylcyclopentadienyl Manganese Tricarbonyl (MMT) has been used for many years in Canada and recently 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. There are currently ongoing debates as to whether or not MMT is harmful to the environment and toxic to humans. However, US Federal sources state that MMT is suspected to be a powerful neurotoxin and respiratory toxin. Oxygenate blending Oxygenate blending adds oxygen to the fuel in Oxygen -bearing compounds such as MTBE , Ethanol and ETBE, and so reduces the amount of carbon monoxide and unburned fuel in the exhaust gas, thus reducing smog. In many areas throughout the US oxygenate blending is mandatory. For example, in Southern California, fuel must contain 2% oxygen by weight. The resulting fuel is often known as ''reformulated gasoline'' (RFG) or ''oxygenated gasoline''. The federal requirement that RFG contain oxygen is being dropped, effective May 6, 2006 {Link without Title} . MTBE use is being phased out in some states due to issues with contamination of ground water. In some places it is already banned. Ethanol and to a lesser extent the ethanol derived ETBE are a common replacements. Especially ethanol derived from biomatter such as corn, sugar cane or grain is frequent, this will often be referred to as ''bio''-ethanol. An ethanol-gasoline mix of 10% ethanol mixed with gasoline is called Gasohol . 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 . Over 3,400 million US gallons (13,000,000 m³) of ethanol mostly produced from corn was produced in the United States in 2004 for fuel use, and E85 is fast becoming available in much of the United States. The use of Bioethanol , either directly or indirectly by conversion of such ethanol to ''bio''-ETBE, is encouraged by the European Union Biofuels Directive. HEALTH CONCERNS Many of the non-aliphatic hydrocarbons naturally present in gasoline (especially aromatic ones like Benzene ), as well as many anti-knocking additives, are Carcinogenic . Because of this, any large-scale or ongoing leaks of gasoline pose a threat to the Public's Health and the environment, should the gasoline reach a public supply of Drinking Water . 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 Sacrificial Anode s. Gasoline is rather Volatile (meaning it readily Evaporates ), requiring that storage tanks on land and in vehicles be properly sealed. The high volatility also means that it will easily ignite in cold weather conditions, unlike diesel for example. Appropriate venting is needed to ensure the level of pressure is similar on the inside and outside. Gasoline also reacts dangerously with certain common chemicals; for example, gasoline and Crystal Drāno ( Sodium Hydroxide ) react together in a Spontaneous Combustion . It is also one of the few liquids that you are not supposed to vomit out of your system because of its tendency to burn your throat. Gasoline is also one of the sources of pollutant gases. Even gasoline which does not contain Lead or Sulfur Compounds produces Carbon Dioxide , Nitrogen Oxide s, and Carbon Monoxide in the Exhaust of the Engine which is running on it. Through misuse as an Inhalant , gasoline also contributes to damage to health. "Petrol sniffing" is a common way of obtaining a high for many people and has become epidemic in many poorer communities such as with Indigenous Australians . In response, Opal fuel has been developed by the BP Kwinana Refinery in Australia, and contains only 5% Aromatics (unlike the usual 25%) which inhibits the effects of inhalation. CURRENT USE The United States uses 360 million US liquid Gallon s (1.36 Gigalitre s) of gasoline each day. Western countries have among the highest usage rates per person, while developing nations like China typically have the highest usage by volume. Some countries, e.g. in Europe, impose heavy Fuel Tax es on fuels such as gasoline, leading to greater efficiency and economy in car design. STABILITY When gasoline is left for a certain period of time, gums and varnishes may build up and precipitate in the gasoline, causing "stale fuel." This will cause gums to build up in the cylinders and also the fuel lines, making it harder to start the engine. Gums and varnishes should be removed by a professional to extend engine life. Motor gasoline may be stored up to 60 days in an approved container. If it is to be stored for a longer period of time, a fuel stabilizer may be used. This will extend the life of the fuel to about 1-2 years, and keep it fresh for the next uses. Fuel stabilizer is commonly used for small engines such as lawnmower and tractor engines to promote quicker and more reliable starting. SUBSTITUTES Main article: Alternative Fuel SEE ALSO
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