A Copper-Lead Bearing Corrosion Test Replacement 971623
The Cooperative Lubrication Research (CLR) Oil Test Engine, usually called the L-38, has been used for nearly 25 years to evaluate copper-lead journal bearing protection of gasoline rnotoroils under high-temperature, heavy-duty conditions. The test is sensitive to aggressive surface active additives that may encourage bearing corrosion. The L-38 also provides an estimate of oil durability, assessing the resistance of an oil to the accumulation of acidic by-products of combustion that could attack copper-lead bearings. However, the L-38 engine dynamometer test uses a heavily leaded gasoline that is no longer representative of the commercial fuels available in North America, Europe, or Japan.
Rather than discard the L-38, this paper describes work to modify the L-38 procedure to run with unleaded gasoline. A series of tests in the current L-38 and in the unleaded L-38 were run on in-house reference oils representative of current International Lubricant Standardization and Approval Committee (ILSAC) GF-2 quality.
In general, the severity of the unleaded L-38 and the standard L-38 is comparable although the unleaded L-38 is somewhat more severe both for bearing weight loss and oxidation of the test oils.