Proper Antioxidant Selection for API SH by Statistical Evaluation in a New Sequence IIIE Screening Test

A bench test has been developed to simulate sequence IIIE engine test viscosity increase. This test was used to evaluate two different alkylated diphenylamine antioxidants in a “marginally formulated” SG oil. Variations in lubricant performance were statistically analyzed. The predicted time required to reach 375% viscosity increase in the sequence IIIE (T375) was found to differ by up to 5 hours for these lubricants containing different alkylated diphenylamine antioxidants. The application of Multiple Test Acceptance Criteria (MTAC) for API SH oils will bring with it the need for a higher level of lubricant oxidative stability. This new bench test can be a useful tool in the selection of high performance antioxidants.