1.1 ,This test method covers determination of the wet filterability of lubricants and hydraulic fluids based upon mass flow rate measurements through a 0.8 ,µ,m membrane after ageing of the fluid in the presence of water. The procedure applies to lubricants and hydraulic fluids that are formulated with American Petroleum Institute (API) Group I, II, III, IV and certain V base stocks. Products formulated with water or base stocks that are heavier than water are out of scope.