The Nissan Motor Oil 10W–30 Lubricating Properties Experimental Studies by the Adsorbed Film Strength Criterion

The article examines current issues related to assessing the lubricating properties of engine oil depending on operating temperature conditions and the degree of oil degradation caused by vehicle mileage. The paper presents the results of experimental research aimed at determining the rupture force of the oil film adsorbed on the friction surfaces of Nissan Motor Oil 10w–30. For this purpose, a specialized tribological testing machine was developed to simulate conditions that closely resemble the real operating environment of components such as the valve train, rocker arms, and camshaft. The experiments considered two varying factors: engine oil temperature and vehicle mileage. The obtained data were processed using mathematical statistics methods, resulting in regression equations in both coded and natural form, describing the dependence of oil film rupture force on the studied parameters. It was found that the rupture force of the engine oil film decreases with increasing temperature, while the highest values of this parameter are observed at approximately 2500 km of mileage. It was also revealed that slightly used oil may exhibit better lubricating properties than new oil due to the accumulation of combustion products with increased dipolarity, which enhances its adsorption ability on metallic surfaces. Based on the research carried out, practical recommendations have been proposed for optimizing engine oil replacement intervals. These include adhering to the manufacturer’s service schedule and mixing a small amount of used oil with new oil to improve lubricating performance. The results can be used to improve diagnostic methods for assessing the operational condition of internal combustion engines.