The progressive decrease in the volatility of gasoline due to the insufficiency of the high-volatility supply has developed a problem of efficient utilization of internal-combustion-engine fuel that requires coordination between the engine and its fuel and a technical as well as economic adjustment between supply and demand. The three channels through which this adjustment tends toward accomplishment are stated and commented upon, consideration then passing to the three main resources from which the components of composite fuels can be drawn. Regarding benzol and alcohol for use as engine fuel, neither can be produced in sufficient quantities in the near future to replace gasoline and this whole field needs greater research attention, but the danger of thus obscuring the necessity of engine adaptations to secure higher thermal efficiency and lessened dependence upon specialized fuels is also pointed out, these being essential elements in a fundamental solution of the engine-fuel problem.