This paper is a study of the changes that have been incorporated in passenger cars sold in the U.S. in recent years to improve fuel economy, and of the significant improvements that have been achieved. Promising areas of new technology are also described that should have the capability of providing further substantial fuel economy improvements. Market acceptance, economic considerations, potential government actions and other factors that may affect fuel economy are also discussed. Although this study is focused on U.S. passenger car developments, the results should also be of relevance in Europe. For consistency with U.S. legislated requirements, fuel economy values in the paper are in miles per U.S. gallon; corresponding fuel consumption figures in litres/100 km are also shown.