THE PAPER is a preliminary report on a study of engine oil-filters made at the University of California Agricultural Experiment Station in connection with research on the effect of character and condition of lubricant on bearing wear. It is similar in its general character to the papers, presented at the 1924 Semi-Annual and the 1925 Annual Meetings, giving data on air-cleaner tests made under the direction of the author.
To determine what the engine-crankcase oil-filter removes, a number of used filters were obtained, principally from vehicles used by the California Highway Commission, the dirt and filter material removed and incinerated, and the ashes weighed and chemically analyzed. The results of this work are tabulated and the quantity of ash remaining after incineration serves as a measure of the solid foreign matter removed from the oil. Practically all of this was abrasive material, consisting of silica, iron, lead and copper in determinable quantities, with traces of tin, manganese, zinc, chromium, magnesium and antimony.
To find a means for evaluating the service of an oil-filter in reducing engine wear, a test was made on two automobiles after each had been given about 10,000 miles of approximately equivalent use, during which one engine had the oil-filter bypassed. The average wear on the piston-rings was approximately twice as much on the machine without the filter.
How the oil-filter affects draining the crankcase was studied on a trip of 10,025 miles in midsummer across the United States and back to the Pacific Coast. Viscosity tests gave practically identical curves for the two trips and showed that the low point was reached before a new charge of oil had been in use for 200 miles and did not change appreciably thereafter. The acidity rose rapidly in the first 200 or 300 miles after draining and remained almost constant thereafter.