A Test Procedure for Evaluating Temporary-Shear Loss of Engine Lubricants

Temporary shear loss characteristics of multigraded engine oils were measured in a newly developed engine oil pump rig. Correlations of the results with high pressure capillary viscometry data indicate that the test apparatus generates shear rates in the range of 2-3 × 10⁵ s^-1. One advantage of this technique over similar mechanical approaches is that the test rig causes virtually no permanent shear degradation. Test results are reported for a variety of polymer types, and the relationship of permanent and temporary shear losses is discussed.