Predicting the Shear Stability of Multigrade Engine Oils from Bench Tests

Engine oil shear stability data from six U.S. and two European car fleets have been obtained using 13 ASTM Reference Oils. These data were obtained to serve as the basis for evaluating the ability of laboratory tests to predict the shear stability of multigrade engine oils in service.

Four types of laboratory bench tests and three different laboratory engine tests were evaluated in an initial program. Based on the results of these tests, additional programs are under way using diesel injector rigs and single-cylinder motored engines in an attempt to improve correlation with the field data. A tapered bearing shear stability tester, not included in the initial program, is also being evaluated. In addition, some recent shear stability activities by the Cooperative European Council are summarized briefly.