Statistical Analysis of HTHS Viscosity Rating of Present-Day Engine Oils

Abstract

The article describes the processes of degradation of five engine oils offered by different manufacturers but belonging to the same SAE class of viscosity. The direction and intensity of changes in high-temperature high-shear (HTHS) viscosity have been analyzed. As part of the experiment, the changes in engine oils occurring during actual operation have been observed. All engine oils were operated in passenger cars of a uniform fleet of 25 vehicles. The curves of changes in these engine oils are of similar shape, and the HTHS viscosity in the oil groups after 12 months, relative to the HTHS viscosity of fresh oil, increased by ∼10%. The limit values were exceeded in two cases. Statistical analysis assisted in confirming the significance of changes in viscosity between measured oils. The obtained results have led to the development of a statistical model to calculate average predictive values of HTHS viscosity for a given mileage. The results may facilitate decision making regarding the service life of engine oils.

Keywords:

• Oil condition monitoring
• lubricant properties
• high-temperature high-shear (HTHS)
• modeling
• degradation
• reliability

Acknowledgments

The authors thank the Director of the Oil and Gas Institute, Prof. Maria Ciechanowska, PhD Eng, and acting as Deputy Director for Oil Technology, Wiesława Urzędowska, MSc, for the opportunity to perform the tests. All laboratory tests for this study were conducted at the Oil and Gas Institute in Kraków, the National Research Institute.

Additional information

Funding

This publication was funded by appropriations of the Faculty of Commodity Science, Cracow University of Economics, within the framework of grants to maintain the research potential.