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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.

The methodology for the acquisition of proportional samples of vehicle engine exhaust gases is presented. The mini-CVS technique used is shown to correlate with full-scale CVS equipment. On the road data for regulated emissions of 15 cars are compared with an earlier survey. These data were obtained over a wide range of operating conditions including urban, rural and motorway drives. Gas chromatographic techniques have been applied to determine the emissions on the road of a range of non-regulated hydrocarbons i.e. aromatics, saturated and unsaturated species. The mini-CVS technique together with a minidilution tunnel for the determination of particulate emissions from diesel engined vehicles is described and results from light-duty and heavyduty vehicles presented.