Spark-ignited gasoline engines are being designed with higher compression ratios using high-swirl, fast-burn combustion chambers and extensive use of electronic controls. These factors, together with the trend to lower lead levels and increasing use of unleaded gasoline, will affect antiknock requirements. Gasoline volatility will be optimized to provide satisfactory performance with available refinery components. The effects of these factors on future gasoline quality requirements are reviewed. The potential for oxygenates as transportation fuels is also assessed.Continued emphasis on fuel economy will result in increased dieselization. This, together with the trend toward heavier crude oils and more catalytic cracking, will result in diesel fuels with lower cetane number, higher final boiling point, and increased density and viscosity. Test data indicate that the effects of these changes on engine performance should be minimal.Expected changes in worldwide industry engine oil specifications are described, along with a description of specific engine builder tests designed to evaluate a particular performance feature. The effect of types of base stocks which are applicable to future oils are reviewed. These include solvent-refined, hydroprocessed and synthetic stocks. The role played by various types of chemical-addition agents are also included in this discussion. The expected changes in future engines and their effect on future engine oils are covered. Finally, the most important engine oil performance parameters required for the future are reviewed.