Future U.S. demand for motor fuel used by passenger cars and light trucks will be met with unleaded gasoline and automotive diesel fuel. Long term, new raw materials -shale oils, tar sands and coal liquids, or methanol - may become available but, at least to the year 2000, conventional crude oil will predominate. If crude oil supply is not interrupted, the U.S. refining industry will be able to meet expected motor fuel demand with processing technology available now, and largely with facilities already installed. However, proper matching of future vehicles and fuels can significantly increase the efficiency with which crude oil is utilized. The refinery gasoline pool should be proportional among at least two octane grades, but gasoline-powered vehicles should be designed to a single octane target near the economic optimum of about 89 (Research + Motor)/2 octane number to achieve maximum vehicle-miles per barrel of crude oil. Because diesel vehicles attain higher miles per gallon, adding them to the vehicle inventory -within certain limits - further increases overall efficiency of crude oil utilization for transportation. However, availability of kerosene for winterizing automotive diesel fuel is limited, and fuel systems of these vehicles should be designed so that they can operate effectively in cold climates on fuels treated with wax-modifier additives for best utilization of light distillate components.