A methodology was developed for estimating the relative fuel efficiency of spark ignition engines from EPA vehicle certification data. The methodology is illustrated for 1978 and 1979 four cylinder engines. An empirical model was developed expressing variations in vehcile weight specific fuel comsumption resulting from variations in the vehicle parameters. Regression analysis was used to estimate the model coefficients. The coefficients were then utilized to achieve a statistical normalization of vehicle weight specific fuel consumption to minimize differences among vehicles. Finally engine quality indicators were derived for ranking automobile manufacturers and for ranking individual engine types.