ABRASIVE material can be maintained at the lowest concentration by circulating the lubricating oil through the filter element at a high rate.
High flow rates can be obtained by shunt operation, high lubricating oil temperatures, and by maintaining a high pressure drop across the filter element.
For intermittent-duty service, it is important to have rapid warm-up of the oil in the filter body, which can be aided either by attaching the filter body to the engine or by installing it in close proximity to the engine and passing through the filter case all or nearly all the oil flow, while maintaining a safe pressure drop with an internally built relief valve.
For test purposes, it is only necessary to have a method of oil solids content determination that is reproducible and that will remove more of the solids than any of the filters being tested. There is still a need, however, for rigid definition of the important types of solid contaminants found in lubricating oil and standardization of accurate, reproducible methods for the quantitative determination of such contaminants.