Evaluation of Diesel Engine Lubricants by Micro-Oxidation 890239
The micro-oxidation test, originally developed at Penn State, has previously been used to study the deposit forming tendency of diesel engine lubricants both at Penn State and Caterpillar using deposit levels and aggregate production of sludge precursor high molecular weight polymers to compare the oils. Researchers at General Motors have used the micro-oxidation test to study the kinetics of the oxidation induced deposit forming reactions for certain basestocks and partially formulated lubricants. In this paper, we begin with reporting the procedural refinement of the micro-oxidation test. We then illustrate how we have developed a method based on first order kinetics deposit forming reactions to rank the relative deposit forming tendency of lubricants. We show how the Arrhenius relationship can be applied to the oxidation reactions of fully formulated lubricants at temperatures consistent with those encountered in the piston ring belt area and top land of heavy-duty diesel engines. We then present the correlation we have achieved between the micro-oxidation results and full-scale engine tests for CD, marine, and railroad oils. We conclude with a discussion on the potential for the development of the micro-oxidation test to achieve correlation with other full-scale engine tests and the inherent benefits.