FOREIGN MATERIAL IN USED OIL: ITS EFFECT ON ENGINE DESIGN 250004
Studies of samples of used engine-oil under the microscope show that the carbonaceous material is extremely finely divided and that the particles are held together loosely by oxidized oil. Dust particles in the oil can be distinguished from other foreign material by means of photographs taken with polarized light. Examination of a number of samples shows that the dust particles circulating with the oil are small in comparison with those drawn in through the carbureter intake, indicating that they have been pulverized on the cylinder-walls.
The results of tests indicate that air-cleaners are of direct benefit, but the use of other devices to prevent dilution and to keep the oil free from foreign material is equally desirable. Oil-screens cannot be expected to remove any but the coarsest material, such as lint; hence they should be of fairly coarse mesh and of liberal area, in order to provide a free flow of oil at low temperatures. They should also be self-cleaning.
