A circulating oil stream cleaner wherein oil to be cleaned is passed through filter medium to remove particulates carried by the circulating oil and through an evaporator unit having a flat, inclined, evaporation surface comprising a top surface of a heat conductive heating block with an electric heater probe therein and positioned closely beneath the heating surface and, with the circulating oil being conductively heated as it passes beneath the heating block, up a frontal end of the heating block and cascades onto and spreads as a film over and then off the heating surface of the heating block through an exit port of the evaporator unit; an evaporation chamber provided above the heating surface allows heated air to circulate over and convectively heat the film of oil and to escape with entrained water and volatiles.
