Ethers, like alcohols and phenols are oxygenated derivatives. An ether has two hydrocarbon groups bonded to the oxygen atom. Diethyl ether (also called simply ether) is the most common variety. It is widely used as a solvent and as a volatile, combustible starting fluid for engines. Methyl-tert-buthyl-ether (MTBE) is used in gasoline to boost the octane rating and to decrease the toxic emissions in the exhaust.