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High viscosity index(HVI) petroleum base stock, with excellent temperature-viscosity characteristics, oxidation resistance, and low-evaporation properties, offers advantages as the base stock for high fuel economy engine oils, particularly because of its low-friction properties in the boundary and/or “E.H.L (Elastohydrodynamic Lubrication)” area due to its rheological characteristics. This research evaluated HVI base stock's low-friction properties. Upgrading the oil from 5W-30 to 5W-20 was also investigated. The friction properties of the HVI base stock were measured by a unit friction platform. The results show a 28% reduction in friction coefficient compared with the conventional, solvent refined oil, which is attributable to the high-pressure viscosity of the base oil.

A high viscosity index (HVI) petroleum base stock (VI=125), which is produced by a severe hydrocracking process, has been used in formulating an advanced SAE 5W-30 oil meeting API SG, EC-II and current ILSAC performance requirements in order to demonstrate potential fuel economy benefits of this oil. The oil was formulated by blending the HVI base stock with a small amount of a solvent-refined base stock to obtain an “optimal aromaticity”, a dispersant VI improver, an optimized combination of detergent and inhibitor, and a conventional ashless friction modifier. The fuel economy performance of this oil has been compared to that of a similarly formulated solvent-refined SAE 5W-30 oil using the Sequence VI test, a motored engine friction test, a new fired/motored friction test, and the EPA road simulator fuel economy test. The SAE 5W-30 HVI oil exhibited an improved fuel economy performance in the above tests, despite of higher HTHS viscosity of the HVI oil.