gasoline (gàs´e-lên˝), light, volatile fuel oil; called petrol in Britain. A mixture of HYDROCARBONS obtained in the fractional DISTILLATION and "cracking" of PETROLEUM, it is used as a fuel for INTERNAL-COMBUSTION ENGINES, for cooking, and as a solvent. The quality of gasoline used in engines is rated by OCTANE NUMBER. To increase octane rating, additives containing lead were once widely used. Because of the health hazard of lead as an environmental pollutant and the harmful effect it has on pollution-control devices, however, AUTOMOBILE design and gasoline composition were changed. Lead additives are now banned in the U.S. Compounds such as methyl tertiary butyl ether (MTBE), which raises octane ratings and promotes more thorough combustion, and ethanol, used in GASOHOL, are now added to reduce pollution. Detergents are added to clean fuel injectors and improve engine performance. Alternatives to gasoline as a vehicular fuel, such as NATURAL GAS and electricity from storage batteries, have also been used on a small scale, particularly in urban areas, where distances are shorter and air pollution greater.
