Experimental Evaluation of the Tribotechnical Properties of Engine Oils for Combine Harvesters

A four-ball extreme pressure test has been performed to study and evaluate the tribotechnical properties of motor oils. The studies have shown that the tribotechnical properties of the engine oil stored in the crankcase during the winter period exhibit a significant change. The average ball wear level has shown a 40% increase compared with that observed in the case of new oil. The average ball wear diameter for the oil samples taken from the combine engines in autumn amounted to 0.5 mm, whereas the average ball wear diameter for the oil samples taken from combine engines in spring amounted to 0.7 mm. When testing new semisynthetic engine oil, the average ball wear diameter varied within 0.48 ± 0.04 mm. It is assumed that the boundary layer formed by the oil is weaker, which causes an increase in the risk of its breaking and sealing the friction pores.