Abstract: An industrial oil reconditioning system forces dirty oil through a three-stage filter which usually includes a first stage comprising a blend of relatively flexible fibers and rigid fibers, a second stage which is all flexible fiber material, and a third stage, preferably of animal fiber. As the oil is forced through the system, under pressure, the fibers of the first and second stages are compressed. The fibers of the first and second stages are cut to a length which causes a weaving or matting during compression to prevent channels from forming in the filter through which oil might pass without being cleaned. The heat of the oil may be precisely controlled at different points in the system to thin the oil, to break emulsions, and to vaporize contaminant fluids. The filtering materials and temperatures may be varied depending upon the type of oil and contaminants being processed. Most industrial oils can be satisfactorily cleaned with one pass through the system.