Oxygenated ethers and alcohols are blended with gasoline to increase octane number and to fight air pollution problems. These oxygenates have replaced alkyl lead and other metal-containing compounds in gasoline because the use of compounds such as tetraethyl lead (TEL), tetramethyl lead (TML), and methylcyclopentadienyl manganese tricarbonyl (MMT) in gasoline has created air pollution problems. The emission of their combustion products from vehicle exhausts creates atmospheric pollution causing serious health hazards. The oxygenates used are methyl tertiary-butyl ether (MTBE), ethyl tertiarybutyl ether (ETBE), tertiary-amyl methyl ether (TAME), tertiary-amyl ethyl ether (TAEE), diisopropyl ether (DIPE), methyl alcohol, ethyl alcohol, and tertiary-butyl alcohol (TBA). Among these oxygenates, MTBE appears to be the most effective choice because its physical, chemical, and thermal properties are compatible with those of gasoline, especially in the boiling range where gasoline typically shows lowest antiknock characteristics. In this chapter, the blending characteristics of a number of ether and alcohol oxygenates are presented.