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While standardized laboratory-scale wear tests are available to predict the lubricity of liquid fuels under ambient conditions, the reality is that many injection systems operate at elevated temperatures where fuel vaporization is too excessive to perform the measure satisfactorily. The present paper describes a High Pressure High Frequency Reciprocating Rig (HPHFRR) purposely designed to evaluate fuel lubricity in a pressurized environment at temperatures of up to 300°C. The remaining test parameters are identical to those of the widely standardized High Frequency Reciprocating Rig (HFRR). Results obtained using the HPHFRR indicate that wear rate with poor lubricity fuels is strongly sensitive to both temperature and oxygen partial pressure and may be orders of magnitude higher than at ambient conditions. Surprisingly however, wear rate was found to decrease dramatically at temperatures above 100°C, possibly due to evaporation of dissolved moisture.

Four bench oxidation tests, the penn state microoxidation test, the thin film oxygen uptake test (TFOUT), ASTM D-2112 and ASTM D-2272 rotating bomb tests (RBOT), were evaluated for their ability to predict the oxidation performance of motor oils in the ASTM Sequence III-D and III-E engine tests. Based on comparative results for a series of oils for which we have III-D, III-E or other engine test data, the Penn State microoxidation test gave the best overall prediction.