Abstract: A cleaning method for removing oils, grease, machining debris and like substances from machine parts and other objects includes a wash tank containing a wash solution, rinse tanks for rinsing the washed objects, and an oil separator containing a concentrated detergent solution for separating oil and detergent in the used wash solution from each other. The separated detergent is returned to the wash tank for further parts cleaning, and the separated oil may be reused for machining purposes. The apparatus automatically maintains the liquid in the wash tank and rinse tanks in an effective condition to satisfactorily clean oily objects.