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Six European vehicles fitted with carbon canisters have been tested under severe conditions to establish if evaporative losses of volatile organic compounds occur under European driving conditions - so-called “running losses”. The programme entailed the development of a point source measurement technique which has a number of advantages over other methods currently in use. Following the development and validation of the measurement technique, the six vehicles were tested at 28C over a range of driving cycles on a gasoline with a Reid vapour pressure of 90 kPa. None of the vehicles exhibited classical running losses, i.e. losses during higher-speed driving. This was due to the effectiveness of canister purging in these conditions. However, significant volatile organic compound (VOC) losses were observed for several vehicles during idle after a period of driving had heated the fuel. Substantial car-to-car variation was observed in the losses obtained.

The spread of octane requirements due to tolerances in engine manufacture has been investigated to indicate the potential improvement in fuel economy which could be achieved by making better use of the available gasoline octane quality. The wide spread of octane requirements in the 48 cars studied resulted in “octane waste”, a measure of the inefficient use by engines of the available octane quality. The average waste was three octane numbers and is associated with variations in compression ratio. The wasted octane can be made available to improve fuel economy through tighter control of manufacturing tolerances on combustion chamber volumes.