An automotive powertrain includes a basically conventional piston engine, a continuously variable ratio transmission, engine speed and power sensors and a feedback control system. The control system adjusts both the transmission ratio and the throttle valve in the engine carburetor or fuel metering system in response to the position of the accelerator pedal and in response to engine power output and crankshaft speed as measured by the engine sensors. The transmission provides extreme overdrive gear ratios which allow the engine to be operated at wide open throttle even during moderate cruising, and, in addition, the engine carburetor or fuel metering system is calibrated to deliver to the engine a stoichiometric air-fuel mixture which is combined, before combustion, with a special proportion of recirculated exhaust gas. As a result of the control system's implementing extensive wide open throttle engine operation with the above mentioned intake charge composition, many combustion variables are optimized to produce exceptional fuel economy.