The Effect of Gasoline Volatility on Emissions and Driveability

The volatility of motor gasoline has always been a key factor in good car performance. It continues to be important to the driveability and emissions of late model cars equipped with exhaust and evaporative control systems. Three research studies have helped to define the role of volatility in late model vehicles. The first, a consumer reaction survey, shows that driveability in cold weather is markedly improved by high mid-fill and back-end volatility. Results from the second program indicate that cars with exhaust and evaporative control systems will perform satisfactorily on fuels of current front-end volatility levels. There will not be a problem with odor in a garage even with fuels of high front-end volatility. Also, varying front-end volatility from low to high levels did not significantly increase the average start-up time for a group of eight cars under hot start conditions. The third study indicates that fuels of high front-end volatility give lower exhaust hydrocarbons than fuels of lower volatility at 40°F and 70°F. Now, in addition to the need for high volatility for start-up in cold weather, there is the added incentive of lower exhaust hydrocarbons.