PURPOSE: To display a speed change shift position in the best rate of fuel consumption, by obtaining the present driving horsepower and calculating necessary torque in each speed change position from the present horsepower then obtaining a fuel consumption rate in each speed change position from an engine speed and the necessary torque.

CONSTITUTION: Signals from a car speed sensor 40, engine speed sensor 36 and an air flow meter 14 are input to a digital control circuit 42. The circuit 42 outputs a valve open timing signal to an injector 28 while displays the best shift position to a digital display device 56. An engine load is obtained from an engine speed signal and an intake air amount from the air flow meter, and engine torque is calculated from a map to calculate both an engine speed and the present driving horsepower. Then necessary torque in accordance with each speed change position is obtained, and a fuel consumption rate in each position is obtained from the map, then the speed change shift position in the best rate of fuel consumption is displayed.