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Engine oil viscosity loss was investigated in highway service and in ASTM D-3945 Procedure A (diesel injector) shear stability test. The six oils involved contained various viscosity index improvers and had D-3945 100°C kinematic viscosity losses ranging from low to high. The losses in service were highest for an oil with one of the lowest D-3945A viscosity losses. D-3945A also did not correlate with service using 150°C high shear viscosity losses. D-3945A shearing severity was modified over a wide range, but it still did not rank oils like highway service. Results indicate a need for a more meaningful viscosity-loss bench test.

A method has been developed for expressing ASTM Sequence IIIE oxidative thickening in terms of test hours to 375 percent viscosity increase (PVI), instead of by PVI at 64 hours, for use in data handling. Expressing results as hrs-to-375 provides a needed transformation for PVI, and enables clearer and more accurate tracking of PVI results. The method has been approved within ASTM for use in proposed Severity Bias Estimate and Multiple Test Acceptance Systems. Use of hrs-to-375 is expected to be required soon.

This paper describes an engine oil test that uses an electrical contact method to determine the loads at which hydrodynamic lubrication is lost in an actual automotive journal bearing. The test is calibrated using newtonian oils so that the effective viscosities of non-newtonian test oils can be determined and compared to those of newtonian oils of specific viscosity grades.

The frictional response of an engine to a particular engine oil depends on the combined effects of the oil’s viscosity and additives which modify rubbing friction during boundary lubrication. A single-cylinder engine friction test is described which measures the frictional characteristics of an oil. These frictional results are integrated with high shear rate viscosity measurements, enabling the individual effects of viscosity and additives on friction level to be viewed separately.