However, this method does not correspond especially well to practical conditions. In this test, the formation and decay of the surface foam is observed ( ÖlChecker Spring 2002). This involves blowing air through a porous stone into the oil sample in order to produce foam. In the past, OELCHECK used only the method specified by ASTM D 892 or ISO DIS 6247 to determine the tendency of gear oils to form surface foam.
