The low-temperature pumpability performance of multigrade engine oils was evaluated in several United States and European engines. Test oils included both experimental formulations and commercial service station oils; test temperatures ranged between -20 and 0 F.
The time for oil to reach engine rocker arms after startup at -15 F and -20 F was not related to low-temperature lubricant properties such as pour point and Brookfield viscosity. Pumpability (that is, oil gallery pressurization rate) of the oils improved markedly in successive cold-temperature starts, probably because of fuel dilution and shearing of microstructures in the oil. Engine design features can significantly affect pumpability performance.