William E. Moehle

Utilizing the TEOST MHT® to Evaluate Fundamental Oxidation Processes in Low-Phosphorus Engine Oils

The thermo-oxidation engine oil simulation test (TEOST)® MHT protocol was used to generate information on deposits and the formation of polar volatile organic compounds. Fourier transform IR (FTIR) spectroscopy was then used to analyze the level of oxidation in recovered TEOST® used oil as well as in the collected volatiles. Data was generated comparing different antioxidant systems in molybdenum-containing and molybdenum-free low-phosphorus engine oil formulations. The results show a surprising difference in deposits, volatiles, and carbonyl oxidation based on the presence or absence of molybdenum and also based on the type of antioxidant system selected. The amount of volatiles produced in the TEOST® is related to well-established oxidation mechanisms and also explains specific oxidation processes sometimes seen in Sequence III engines. A mathematical definition of antioxidant effectiveness or “robustness” is proposed that combines TEOST® deposits and volatiles measurements with FTIR carbonyl oxidation measurements. These results strongly suggest that an analysis of TEOST® used oils and volatiles may provide valuable information regarding oxidation in other bench tests as well as potentially in fired engines. Presented at the STLE Annual Meeting in Las Vegas, Nevada May 15-19, 2005 Review led by Cyril Migdal

A Review of Engine Oil Oxidation Bench Tests and Their Application in the Screening of New Antioxidant Systems for Low Phosphorus Engine Oils

A review of current oxidation and deposit bench tests used for the evaluation of engine oil performance will be presented. Some of the more meaningful tests will be utilized to evaluate a number of antioxidant systems for oxidation and deposit control capabilities in engine oils formulated with 470 ppm of ZDDP-derived phosphorus. The antioxidant components are selected from a series of commonly used and commercially available materials plus one new developmental component. These components include an organo-molybdenum compound (MoDTC), an alkylated diphenylamine (NDPA), a conventional hindered phenolic (HPE), a high performance hindered phenolic (MBDTBP), and a new multi-functional boronated MBDTBP. The performance of these fully formulated engine oils will be ranked in the selected bench tests in order to highlight the benefits of each antioxidant system under evaluation. The results point to significant benefits with the molybdenum- and boronated-systems, or mixed molybdenum-/boronated-systems, for oxidation control, while systems containing NDPA and MBDTBP are favored more for deposit control. Unique and superior performing antioxidant systems will be recommended for screening in fired engine and bench wear tests.