The effect of adding Oxygenates to the fuel, on exhaust emissions and fuel consumption, was evaluated. Chassis dynamometer tests (ECE + EUDC) were carried out on six petrol cars. Three of the cars were fitted with three way catalysts. The fuels had been oxygenated by adding 10 % MTBE, 15 % MTBE, and 5.2 % Ethanol. Test results show that oxygenates in the fuel reduce emissions and fuel consumption. Of the fuels investigated, addition of 15 % MTBE gave most benefits with the following reductions in emissions:- CO: 15 - 30 %, NOx: 1.3 - 1.7 %, THC: 10 - 20 %, CO2: 1.0 - 4.0 %, Reductions in fuel consumption with 15 % MTBE were 1.3 - 1.7 % for non catalyst cars and 3.2 - 5.2 % for catalyst cars.