It is generally accepted that the improvement of the viscosity-temperature relationship by the addition of long chain molecules (LCM) to lubricating oils, at low rates of shear, is practically lost at high rates of shear.
It is the aim of the present work to show that, although the viscosity of oils containing LCM does fall with increasing rates of shear, the V. I. improvement found at low rates of shear is maintained and even increased at high rates of shear provided the lubricant is classified as a lower viscosity oil.
Furthermore, assuming that the multigrade oils are mixtures of two independent phases and that each phase responds independently to temperature and rate of shear, it is concluded that these oils are superior to simple mineral oils in many other respects.