Method and apparatus for improving the fuel economy of a vehicle of the type having a vehicle electrical system that includes a generator senses a vehicle voltage of the vehicle electrical system during determined intervals, and supplies an offset current from an external source of electrical energy to the vehicle electrical system in response to the sensing of a vehicle voltage of the vehicle electrical system. In this manner, the electrical power output of the generator, and its effect on fuel consumption, are reduced in response to supplying of the offset current. A source of electrical energy external to the electrical system of the motor vehicle is controlled by an electronic control unit coupled to the source of electrical energy. A power converter receives on and off commands from the electronic control unit in response to vehicle voltage measurements by the electronic control unit.