An automotive vehicle having improved fuel economy is equipped with a
drive system having a primary internal combustion engine and an auxiliary
internal combustion engine of smaller size and better fuel economy than
the primary engine. The primary engine is adapted to take the vehicle to
its cruising speed, at which point the auxiliary engine is activated and
interacts by way of an automatic clutch system to power the vehicle while
the primary engine is disconnected from the drive system and throttled
down.