Oxygenated chemical compounds contain oxygen as a part of their chemical structure. The term usually refers to oxygenated chemical compounds added to fuels. Oxygenates are usually employed as gasoline additives to reduce carbon monoxide and soot that is created during the burning of the fuel. Compounds related to soot, such as polyaromatic hydrocarbons (PAHs) and nitrated PAHs, are also reduced.

The oxygenates commonly used are either alcohols or ethers:

• Alcohols:
  • Methanol (MeOH)
  • Ethanol (EtOH); see also Common ethanol fuel mixtures
  • Isopropyl alcohol (IPA)
  • n-Butanol (BuOH)
  • Gasoline grade tert-butanol (GTBA)
• Ethers:
  • Methyl tert-butyl ether (MTBE)
  • tert-Amyl methyl ether (TAME)
  • tert-Hexyl methyl ether (THEME)
  • Ethyl tert-butyl ether (ETBE)
  • tert-Amyl ethyl ether (TAEE)
  • Diisopropyl ether (DIPE)