Browse Publications Technical Papers 2004-01-2985
2004-10-25

Development of a Bench Test to Predict Oxidative Viscosity Thickening in the Sequence IIIG Engine Test 2004-01-2985

Of all the performance tests in the current International Lubricant Standardization and Approval Committee (ILSAC) GF-3 and GF-4 categories, the Sequence IIIF and Sequence IIIG are among the most difficult for the formulator. The Sequence III engine dynamometer tests place a premium on oxidation, high-temperature deposits, and valve train wear control. Besides appearing in the North American Passenger Car Motor Oil (PCMO) specifications, the Sequence III is required for European gasoline engine oils, for American Petroleum Institute (API) diesel engine oil categories, and for base oil interchanges (BOI) among licensed engine oils.
The ability to screen antioxidants for the Sequence III is of special interest for developers of engine oil technology. Antioxidants are the single most expensive component and the search for cost-effective oxidation control is among the top technical hurdles for the North American PCMO categories. Given the engine testing costs for formulation development and base oil interchanges, an effective Sequence III bench test is of paramount importance. Further, it has become increasingly obvious that a single antioxidant is not the most effective solution in all base stocks.
We have developed an oxidation bench test to predict the oxidative viscosity increase in the Sequence IIIG engine test. Hours to rapid oxygen uptake in the bench test were found to predict Sequence IIIG viscosity increase reasonably well. Our bench test has been used to run full-factorial antioxidant matrices in a variety of base stocks. Main effects and interactions were observed and a Sequence IIIG viscosity increase model was developed.
This paper summarizes the bench test development and the predictive Sequence IIIG viscosity increase model that resulted.

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