Search Results

A vane pump rig of the type used in ASTM D-2882 was used to study the permanent and temporary shear loss characteristics of hydraulic fluids containing a variety of VI improvers. The influence of polymethacrylate VI improver molecular weight on performance was studied. Severity of hydraulic oil service was assessed relative to that tor automotive engine oils, and the suitability of common VI improvers is discussed. It was shown that shear stable polymethacrylate VI improvers can provide a high level of performance for extended periods of time.

The role of non-Newtonian fluid characteristics in lubricant performance was studied in a variety of V.I. improved lubricants. It was shown that proper choice of V.I. improver can yield a lubricant which undergoes both small temporary and permanent viscosity losses, thus giving nearly Newtonian behavior but with high and low temperature performance advantages over straight mineral oils. In hydraulic fluids, it was shown that different V.I. improvers resulted in varying amounts of internal leakage in both vane and internal gear pumps. In the case of vane pumps, the favorable Newtonian characteristics of shear-stable V.I. improvers assured outstanding pumping performance. It is believed that control of transmission leak-down was primarily responsible for the favorable influence a shear-stable V.I. improver had on the maximum transmission sump temperature at which the wide-open throttle 2-3 upshift will take place.