MTBE in gasoline

The abbreviation MTBE refers to methyl tertiary butyl ether—a volatile, water-soluble, oxygencontaining,colourless liquid with an ethereal odour. In Europe, it is used mainly to boost octane rating, especially in unleaded and lead-replacement grades. It is being used in increasing amounts to compensate for octane rating lost with the reduction of benzene, aromatics and olefin contents of gasoline and the phase-out of leaded gasoline which are required by new EU fuels legislation.

MTBE is one of a number of oxygenated compounds (including other ethers and alcohols) which can be used in gasoline. EU Directive 98/70/EC permits gasoline to contain up to 15% v/v MTBE. In fact, although the use of MTBE is widespread, the concentrations used in Europe are nearly always much lower than this, on average approximately 2–3% v/v.