Deterioration Experiments of Antifriction and Anti-wear Properties of Vehicle Engine Oils

Antifriction and anti-wear performance is the key to determine the oil change cycle of vehicle engine oils. Based on driving tests and sample collection of engine oils, the evolution rules and degradation mechanisms of antifriction and anti-wear performance of vehicle engine oils are studied by test methods. Firstly, the collected oil samples are tested according to the standard requirements of oil changing, and it is found that the engine oils in the running test is within the oil change index limit when reaching the oil change cycle. Then, the tribological performance tests of the oil samples are carried out using SRV micro motion friction and wear testing machine and four-ball friction and wear testing machine. The results show that there is a service range or time with the best tribological performance during the service life cycle of the engine oil, where the friction coefficient is the smallest and the wear volume is the least. Finally, wear track is characterized and analyzed using scanning electron microscopy and EDAX energy spectrometer, and from the perspective of the change of kinetic viscosity of engine oil, the internal mechanism of the deterioration of antifriction and anti-wear performance of engine oil is analyzed. The thermal decomposition, shear fracture and thermal polymerization of base oil molecules are the keys to the change of friction coefficient of engine oil. The main reason for the change of anti-wear properties is the concentration of extreme pressure anti-wear additives and frictional chemical reaction. The research conclusion of this paper has certain theoretical significance and engineering application value for engine oil development and oil change cycle determination. © 2024 SAE-China. All rights reserved.