This paper is based upon the premise that the best way to deal with current constraints imposed upon car engines is by technological advances designed to (1) minimize pollutant emissions, (2) maximize engine efficiency, and (3) optimize tolerance to a wider variety of fuels. A sense of direction for such advances is derived from a critical assessment of the fundamental advantages of reciprocating I.C. engines as prime movers for automobiles, and the review of their recent developments. On this basis it is shown that major impact in this respect could be made by control1ed combustion. Intrinsically, this should involve proper handling of active radicals, the essential elements of the combustion reaction. Practically, this can be achieved by a variety of means, such as charge stratification, exhaust gas recirculation, homogeneous lean burn, combined with enhanced ignition and enhanced auto-catalysis.