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A high shear rate capillary viscometer has been developed. It is suitable for measuring the viscosity of engine oils at shear rates of 105 to 106 s−1 and at temperatures to 150°C, conditions which are within the range experienced by oils in automobile engines. It has proven useful for evaluating the total shear stability of VI-improved oils and is also being used for interpreting laboratory engine friction testing.

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.