The fuel economy data compiled by the U.S. Environmental Protection Agency (EPA) have been analyzed to determine the trends in passenger car fuel economy beginning with model year 1957. This paper adds the 1976 model year data to the historical trend and concentrates on comparisons between the 1976 and 1975 models.Calculation procedures which allow the changes in fuel economy to be determined separately for system optimization, new engine/vehicle combinations, and model mix shifts have been employed in the analysis which compares 1976 models with 1975 models. A wide range of percentage changes was seen for the fifteen manufacturers who were certified in time to be included in the analysis performed for this paper.The net change in fuel economy for the 1976 new car fleet has been estimated at +12.8% compared to the 1975 new car fleet. System optimization is responsible for 8.8% of the improvement and model mix shifts are projected to account for +3.1% of the change. The improvements made on the 1976 models are projected to result in 1976 cars being the most fuel efficient produced since 1957, the earliest model year for which a significant amount of consistent fuel economy data exists.The 17.6 mpg city/highway combined fuel economy projected for the 1976 models is 27% better than the 13.9 mpg 1974 model results which served as the basis for the Presidents Voluntary fuel economy improvement program which requested a 40% gain by 1980.Whether the trend toward improved fuel economy which has been seen with the 1975 and 1976 models will continue in the future primarily depends on the degree of interest in achieving higher fuel economy on the part of the government, automotive industry, and motoring public. Compromises in the areas of cost, styling and acceleration performance could allow substantial improvements on some models. The effect of more stringent emission standards will largely depend on the degree of sophistication used in the design of spark advance systems, fuel metering systems and emission control systems.