Impacts of Fully-Formulated Engine Oils Containing MoDTC on the Tribological Performance of Nitrided Piston Rings Sliding Against Cast Iron Cylinder Bores

摘要

The tribochemical interaction in a nitrided piston ring /cast iron cylinder bore slidingrncontact with two commercial fully-formulated engine oils (ILSAC GF-2 and GF-3rncategory), both supplemented with additional molybdenum dithiocarbamate (MoDTC)rnfriction modifier, was investigated in a laboratory bench test. Test results indicated thatrnthe GF-2 oil could produce a rapid friction reduction while the GF-3 oil maintained arnstable and lower coefficient of friction (μ=0.03) for a longer testing time. The GF-3 oilrnalso generated a lower wear rate compared with the GF-2 oil under the same tribotestrnconditions. Based on the SEM/EDX analyses of wear tracks on the testedrntribo-components, it appears that a synergistic reaction between the major additivesrn(MoDTC, ZDTP and Ca-containing detergent) in the GF-3 oil made a significantrncontribution to its tribological performance compared with the GF-2 oil when slidingrnunder the same test conditions.