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The determination of the total antioxidant capacity of new and used automatic transmission fluids can yield information useful in the study of fluid stability, severity of service and correlation between bench tests and service. The technique is particularly useful in the characterization of the earlier stages of fluid oxidation where parameters such as T.A.N., pentane insolubles and viscosity yield little information. Three fluids from a fleet test manifested different antioxidant decay profiles. Data obtained from a laboratory beaker test indicate that some test conditions can reproduce these decay curves and thus simulate the primary oxidation processes occurring in the transmission in this fleet.

A new method for the determination of antioxidant capacity in lubricants has been utilized for the analyses of new and used engine oil samples. The results derived from these analyses were used for monitoring the antioxidant decay during laboratory and long drain fleet testing and in various correlation studies. The application of the method provided new insights into the nature of the oxidative deterioration of engine oils as a function of type and initial concentration of antioxidant additives, of type of base oil and of test or engine severity.