British petrol
Mixture of volatile, flammable hydrocarbon s derived from petroleum , used as fuel for oil s and fat s.
Gasoline became the preferred automobile fuel because it releases a great deal of energy when burned, it mixed readily with air in a carburetor , and it initially was cheap due to a large supply. Costs have now increased greatly except where subsidized. Gasoline was first produced by distillation . Later processes increased the yield from crude oil by splitting large molecules into smaller ones. Still other methods, such as conversion of straight-chain hydrocarbons into their branched-chain isomer s, followed. The resulting gasoline is a complex mixture of hundreds of hydrocarbons. A gasoline's octane number indicates its ability to resist knocking (premature combustion) and can be altered by changing the proportions of certain components. The compound tetraethyl lead , once used to reduce knocking, has been banned as toxic. Other additives include detergent s, antifreeze s, and antioxidant s. Since the mid-20th century gasoline fumes have been recognized as a major component of urban air pollution . Efforts to reduce dependence on gasoline, which is a nonrenewable resource, include use of gasohol, a 9:1 mix of gasoline and {{link=ethanol">ethanol , and the development of electric automobiles .