A system and method for managing an engine-powered vehicle is provided. When the vehicle is placed in an automatic speed control mode, an electronic controller receives data from the vehicle's engine, transmission, a final drive, and a device which evaluates at least one variable. The electronic controller determines engine rpm and transmission gear as a result of the data received, and automatically up-shifts the transmission and reduces engine speed to reduce fuel consumption when a load on the vehicle is reduced and down-shifts the transmission and increases engine speed when a load is applied.