A Rating System for Viscosity Index Improvers 730484

The purpose of the work reported in this paper was to develop a simple and reliable method of comparing the relative merits of various polymers in a homogeneous sytem of base oils that might be used in multigraded motor oil applications. It was demonstrated that by using consistent methods of tests, comparisons between polymers can be made, that more clearly define the properties of the polymers than methods that have been used in the past. It was determined that in a series of polymers of the same molecular type, those polymers with the lowest molecular weight will have the greatest shear stability. The contribution to low shear, low-temperature viscosity varies widely with variations in molecular type. A rating factor can be produced which is relatively constant for polymers of the same molecular type regardless of molecular weight.