Compositional Effects on the Low Temperature Pumpability of Engine Oils

An in-depth study of the additive and basestock component factors affecting low temperature viscometrics and oil pumpability of multigrade engine oils has been made. Basestock pour points or residual wax contents alone do not predict low shear viscometric properties of the finished oils under slow-cool conditions. Rather, the composition of the wax itself is a key factor with both normal and non-normal paraffins contributing to viscometric increases at low temperatures. It is shown that viscosity index improver and pour depressant selection can prove to be critical in the prevention of oil gelation leading to pumpability failure.

The results of these lab viscometric studies have been confirmed in all weather chassis dynamometer tests on five 4-cylinder overhead cam engines.