Significant Cost of Ownership advantages can be realized by sharing aircraft gearbox oil with the Electrical Power Generating System. These advantages result from the elimination of redundant oil system functions and the utilization of the existing gearbox heat exchanger. The shared oil system concept, whether with an engine gearbox or with an accessory gearbox, offers comparable advantages.General Electric’s “dry cavity” generator design employed in its Variable Speed Constant Frequency Electrical Systems provides a technically acceptable solution to oil sharing. In this design, the oil within the generator, is contained entirely within passages made of engine quality materials. Contamination of the oil due to electrical insulation is not possible.This paper describes the shared oil system, why it is technically acceptable and compares the reliability, and maintainability advantages over an independent oil system. These advantages are applied to the life cycle cost formulas to show the specific advantages to be gained.