A synthetic waste oil was filtered through asym. porous, ceramic membranes (pore size 2.4-200 nm) at 35-75 degrees C and under transmembrane pressures 1.2-6.5 bar before and after a preliminary sedimentation for 3 months. The purifn. of raw oil sample resulted in a redn. of the oil d. by 2.1% and its kinematic viscosity by 65% at a flow ratio of 11.8 L/(h center dot m(2)). No quality changes after filtration of the preliminary purified oil were obsd.