Study of the physical properties of oil contaminants and oil filtration show that present methods of filtration have little effect on a lifter wear problem. Experiments prove that oil additives can influence the effectiveness of conventional oil filters, which are capable of removing particles considerably smaller than their pore size. Lifter wear, therefore, seems to be a function of extended oil drain periods during which contaminants accumulate in the oil and progressive smooth wear occurs. Although present filters are performing adequately, they could be improved by advances in design and in oil formulation so as to minimize contaminant accumulation.
