COMPARISON OF MINERAL AND SYNTHETIC BASE OILS USING CORRELATIONS FOR BENCH AND ENGINE TESTS

Base oil compositional profiles can. have an important impact on a fin ished lubricant's performance in both crankcase and industrial applica tions. The American Petroleum Institute has developed guidelines for d etermining the amount of engine testing needed to modify a licensed ga soline and/or diesel engine oil formulation. The adoption of these gui delines and the need for reliable screening tools for expensive and ti me-consuming bench and engine tests have led to the development of sta tistical predictive models for two current gasoline engine tests and a long-term bench oxidation test. These models can also be used to quic kly compare the ''theoretical'' performance of synthetic base oils to conventional base oils. The models use partial least-squares statistic al analysis to predict the performance of similar lubricants manufactu red with different base oils. To date, models have been developed for predicting the performance of crankcase engine oils in the ASTM Sequen ce IIIE and ASTM Sequence VE engine tests and for predicting the numbe r of hours a turbine oil will withstand the oxidation environment of t he ASTM D943 test. These models use detailed hydrocarbon-type analysis and physical parameters to predict the oil's performance. The models have been particularly useful in comparing products containing convent ional mineral Base oils, re-refined mineral base oils, non-conventiona l high viscosity index base oils, and synthetic base oils.