a lubrication system for an internal combustion engine includes a variable displacement oil pump supported on the engine block and connected to draw oil from the oil pan and to supply pressurized oil to various engine components . the pump defines variable displacement pumping chambers for carrying oil from an inlet to a pressurized outlet . an exemplary embodiment includes a vane pump with a feedback displacement control using pressure from the lubrication system to actuate a slide ring in the pump to control the pump output . numerous features of the pump are disclosed .