Abstract: A drain plug adapter for use in place of a standard drain plug in the crankcase of an internal combustion engine includes two portions. The first portion is a drain plug adapter housing having a cylindrical passage through it in which a ball check valve is mounted. The ball check valve is resiliently biased by means of a compression coil spring into engagement with a rubber O-ring mounted in an annular groove near the upper end of the drain plug adapter to form a valve seat for engagement by the ball under bias of the compression coil spring. A valve body coupler is threadedly attached to the lower end of the drain plug adapter and has a fluid path through it in communication with the passage through the drain plug adapter. The coupler is connected by means of a fluid conduit to an electric motor driven pump for withdrawal oil from the crankcase by creation of a vacuum beneath the ball of the check valve to move it downwardly to permit oil to be withdrawn.