The Role of Hydroperoxide in Engine Wear and the Effect of ZnDDP/Dispersant/Detergent Interactions 872157

Engine wear, particularly that of the valve train, was examined in motored 2.2L and 2.3L engines. Procedures were developed which involved addition of synthetic hydroperoxide to the crank-case oil to simulate fired engine conditions. Cam lobe and follower wear occurred, apparently as a result of direct attack by the hydroperoxide on rubbing surfaces. This type of hydroperoxide-induced wear was identified in a fired bench engine test and in a field test. Similar hydroperoxide-induced wear was also observed in the lesser loaded engine contact areas such as bearings. Phosphorus nuclear magnetic resonance (NMR) has proven to be a useful tool to the understanding of the structure and antioxidant antiwear properties of ZnDDP and its interactions with dispersant/detergent combinations.