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An engine dynamometer test was developed to simulate the effects of high-temperature, high-load driving conditions on the rate of engine oil degradation. The test engine, a 3.4-L 60° V6, is operated at 3000 r/min and 103 Nm load for 125 h at elevated oil and coolant temperatures and without oil additions. Oil samples are collected at regular intervals and analyzed for chemical and physical properties. Results show that five different chemical and physical properties exhibit regular, predictable changes with operating time. By fitting all data to appropriate functional forms, a very precise fit is obtained (r2 typically > 0.97) for the rate of change in each parameter. When these changes are normalized and corrected for oil consumption, their average can be used to calculate an overall Performance Factor.

Radiometric techniques have been developed and successfully applied to journal bearing studies in a unidirectional bearing test machine. These techniques, which involve the detection of wear debris from a radioactive (113Sn) test bearing, were used to determine bearing load capacity with both Newtonian and non-Newtonian lubricants. Results indicate that the radiometric method can rapidly provide information that correlates with other laboratory and engine test data.

Radiometric wear techniques have been applied to determine the effect of fuel-saving engine oils on journal bearing load capacity. A test machine which applied a unidirectional load to a radioactive test bearing was used to evaluate bearing load capacity. The onset of bearing wear with increasing load provided a direct measurement of fluid-film breakdown, which defined hydrodynamic bearing load capacity. From this, an “effective” lubricant viscosity was calculated by comparing the performance of non-Newtonian lubricants to the performance of Newtonian lubricants. Results show that for the oil formulations tested that employ either a low viscosity or a soluble friction modifier to reduce engine friction, there is a high correlation between high-shear viscosity and hydrodynamic load capacity. The use of an insoluble friction modifier resulted in a higher bearing load capacity than expected based on high-shear viscosity.

Radiometric wear measurement techniques have been applied to determine the effect of journal surface finish on journal bearing load capacity. Bearing load capacity was measured by using a test machine that applies a linearly increasing unidirectional load to a radioactive test bearing. The onset of bearing wear provides a direct measurement of fluid-film breakdown, which is used to define hydrodynamic bearing load capacity. By use of a journal that can be located at two different positions on the shaft, the relative difference in load capacity between two journal surface finishes can be measured without the need to disturb the geometry of the bearing. The effect of journal surface finish on bearing load capacity was thereby quantified. In this study, nodular iron journals were prepared to have test surfaces with different levels of surface roughness.