Octane rating in the context of "Gasoline engine"

A filling station (also known as a gas station [US] or petrol station [UK/AU]) is a facility that sells fuel and engine lubricants for motor vehicles. It serves as a local fuel depot and retailer who receive fuel products from refineries (via regular tank truck resupplies), keep the fuels in (typically underground) storage tanks, and distribute individual product to motorist consumers at a daily varied price.

The most common fuels sold are motor fuels such as gasoline (a.k.a. petrol, often as multiple products according to different octane ratings) and diesel fuel, as well as liquified petroleum gas (LPG, i.e. autogas), compressed natural gas, compressed hydrogen, hydrogen compressed natural gas, liquid hydrogen, kerosene, alcohol fuels (like methanol, ethanol, butanol, and propanol), biofuels (like straight vegetable oil and biodiesel), or other types of alternative fuels. Fuel dispensers are used to pump fuel into the fuel tanks within vehicles, gauge the volume of fuel transferred to the vehicle, and calculate the financial cost the consumer must pay. Besides fuel pumps, another significant device found in filling stations and capable of refueling certain (compressed-air) vehicles is an air compressor. However, these are generally used to inflate car tires.

Gasoline (North American English) or petrol (Commonwealth English) is a petrochemical product characterized as a transparent, yellowish and flammable liquid normally used as a fuel for spark-ignited internal combustion engines. When formulated as a fuel for engines, gasoline is chemically composed of organic compounds derived from the fractional distillation of petroleum and later chemically enhanced with gasoline additives. It is a high-volume profitable product produced in crude oil refineries.

The ability of a particular gasoline blend to resist premature ignition (which causes knocking and reduces efficiency in reciprocating engines) is measured by its octane rating. Tetraethyl lead was once widely used to increase the octane rating but is not used in modern automotive gasoline due to the health hazard. Aviation, off-road motor vehicles, and racing car engines still use leaded gasolines. Other substances are frequently added to gasoline to improve chemical stability and performance characteristics, control corrosion, and provide fuel system cleaning. Gasoline may contain oxygen-containing chemicals such as ethanol, MTBE, or ETBE to improve combustion.

Autogas is liquefied petroleum gas (LPG) used as a fuel in internal combustion engines of vehicles as well as in stationary applications such as generators. It is a mixture of propane and butane.

Autogas is widely used as a "green" fuel, as its use reduces CO₂ exhaust emissions by around 15% compared to petrol. One litre of petrol produces 2.3 kg of CO₂ when burnt, whereas the equivalent amount of autogas (1.33 litres due to the lower density of autogas) produces 2 kg of CO₂ when burnt. CO emissions are 30% lower compared to petrol, and NO_x is reduced by 50%. It has an octane rating (MON/RON) that is between 90 and 110 and an energy content (higher heating value—HHV) that is between 25.5 megajoules per litre (for pure propane) and 28.7 megajoules per litre (for pure butane) depending upon the actual fuel composition.

Petroleum naphtha is an intermediate hydrocarbon liquid stream derived from the refining of crude oil with CAS-no 64742-48-9. It is most usually desulfurized and then catalytically reformed, which rearranges or restructures the hydrocarbon molecules in the naphtha as well as breaking some of the molecules into smaller molecules to produce a high-octane component of gasoline (or petrol).

There are hundreds of different petroleum crude oil sources worldwide and each crude oil has its own unique composition or assay. There are also hundreds of petroleum refineries worldwide and each of them is designed to process either a specific crude oil or specific types of crude oils. Naphtha is a general term as each refinery produces its own naphthas with their own unique initial and final boiling points and other physical and compositional characteristics.

A petrol engine (gasoline engine in American and Canadian English) is an internal combustion engine designed to run on petrol (gasoline). Petrol engines can often be adapted to also run on fuels such as liquefied petroleum gas and ethanol blends (such as E10 and E85). They may be designed to run on petrol with a higher octane rating, as sold at petrol stations.

Most petrol engines use spark ignition, unlike diesel engines which run on diesel fuel and typically use compression ignition. Another key difference to diesel engines is that petrol engines typically have a lower compression ratio.

Gasoline additives may increase gasoline's octane rating, thus allowing the use of higher compression ratios for greater efficiency and power, or act as corrosion inhibitors or as lubricants. Other additives include metal deactivators, oxygenates and antioxidants.

Some additives are harmful and are regulated or banned in some countries.

Tetraethyllead (commonly styled tetraethyl lead), abbreviated TEL, is an organolead compound with the formula Pb(C₂H₅)₄. It was widely used as a fuel additive for much of the 20th century, first being mixed with gasoline beginning in the 1920s. This "leaded gasoline" had an increased octane rating that allowed engine compression to be raised substantially and in turn increased vehicle performance and fuel economy. TEL was first synthesized by German chemist Carl Jacob Löwig in 1853. American chemical engineer Thomas Midgley Jr., who was working for the U.S. corporation General Motors, was the first to discover its effectiveness as an knock inhibitor on December 9, 1921, after spending six years attempting to find an additive that was both highly effective and inexpensive.

Of the some 33,000 substances in total screened, lead was found to be the most effective antiknock agent, in that it necessitated the smallest concentrations necessary; a treatment of 1 part TEL to 1300 parts gasoline by weight is sufficient to suppress detonation. The four ethyl groups in the compound served to dissolve the active lead atom within the fuel. When injected into the combustion chamber, tetraethyllead decomposed upon heating into ethyl radicals, lead, and lead oxide. The lead oxide scavenges radicals and therefore inhibits a flame from developing until full compression has been achieved, allowing the optimal timing of ignition, as well as the lowering of fuel consumption. Throughout the sixty year period from 1926 to 1985, an estimated 20 trillion liters of leaded gasoline at an average lead concentration of 0.4 g/L were produced and sold in the United States alone, or an equivalent of 8 million tons of inorganic lead, three quarters of which would have been emitted in the form of lead chloride and lead bromide. Estimating a similar amount of lead to have come from other countries' emissions, a total of more than 15 million tonnes of lead may have been released into the atmosphere.

Methyl tert-butyl ether (MTBE), also known as tert-butyl methyl ether, is an organic compound with a structural formula (CH₃)₃COCH₃. MTBE is a volatile, flammable, and colorless liquid that is sparingly soluble in water. Primarily used as a fuel additive, MTBE is blended into gasoline to increase octane rating and knock resistance, and to reduce unwanted tailpipe emissions.