Abstract: A novel method and system for automatically removing an engine's used lubricating oil and injecting the used oil into the engine's fuel system throughout operation is disclosed. The lube oil removal system includes a removal and injection pump including a spring biased piston forming a chamber on each side. The lube oil removal system also includes a transfer circuit connecting the chambers and a pump control device for controlling the flow between the chambers. The pump control device also controls the flow of used oil from the engine to one of the chambers while a discharge circuit connects the other chamber to the engine fuel system. In a first position, the pump control device blocks the used oil from the engine while connecting the chambers and, in a second position, connects the used oil circuit to one of the chambers while blocking flow between the chambers.