Correlation between Lube Oil HTHS and Techno-Economic Performance and Service Life of a Reciprocating Engine

Abstract

This paper discusses the effect of lube oil high-temperature viscosity on performance indices of high-powered automotive engines (e.g., power, fuel economy and wear rate of friction pairs). Such engines are generally prone to departure from hydrodynamic friction mode in friction pairs, caused by high mechanical load and high lube oil temperature. In this case friction horsepower will depend not only on oil viscosity parameters, but also on properties of anti-wear and anti-friction additives, if any. Moreover, spread in high-temperature viscosity of motor oils belonging to the same SAE group may be great enough. This paper furnishes evidence of existence of optimum high-temperature viscosity level, at which fuel economy reaches its maximum. Dependence of optimum viscosity on engine power conditions is revealed. One of the tasks of this work is examination of how high-temperature viscosity (HTHS) of modern all-synthetic motor oils, belonging to various viscosity classes, correlates with friction and wear characteristics of a high-speed motorcar engine.