Effects of Exhaust Gas Recirculation on the Degradation Rates of Lubricating Oil in a Heavy-Duty Diesel Engine

The specific goal of this project was to determine if there is a difference in the lube oil degradation rates in a heavy-duty diesel engine equipped with an EGR system, as compared to the same configuration of the engine, but minus the EGR system. A secondary goal was to develop FTIR analysis of used lube oil as a sensitive technique for rapid evaluation of the degradation properties of lubricants. The test engine selected for this work was a Caterpillar 3176 engine. Two engine configurations were used, a standard 1994 design and a 1994 configuration with EGR designed to meet the 2004 emissions standards. The most significant changes in the lubricant occurred during the first 50-100 hours of operation. The results clearly demonstrated that the use of EGR has a significant impact on the degradation of the engine lubricant. Specifically, the rate of accumulation of soot was dramatic, and the rate of change of the oxidative stability increased by factor of two as a result of the use of EGR. In addition, it appears that the use of EGR also caused more than a factor of two increase in the rate of accumulation of iron wear metal in the lube oil. These levels of change were apparent, even in the very short duration tests used in this work.