Methyl tertiary butyl ether (MTBE) production has been used in gasoline as an octane booster and oxygenate. It can also be used to make high purity isobutylene for butyl rubber and polyisobutylene production and employed as a solvent and extractant. It is also used medically to dissolve gallstones. MTBE is almost exclusively used as a fuel component in fuel for gasoline engines. It is one of a group of chemicals commonly known as oxygenates because they raise the oxygen content of gasoline.