Factors Affecting the Low Temperature Pumpability of Used Engine Oils

A large number of studies have been published on the low temperature pumpability characteristics of fresh oils; however, less is known about the effects of oil aging on this property. In laboratory viscometric tests, fuel dilution, mechanical shearing, oxidative degradation and oil contaminants were all shown to significantly affect low temperature fluidity of multigrade engine oil formulations sensitive to slow cool gelation. Moreover, the cooling and shear rate applied to the test oil was found to play an important role in the overall impact of these factors. For example, fuel dilution may improve cold cranking viscosity while degrading slow-cool MRV performance. These laboratory viscometric studies have been supplemented by full scale All-Weather Chassis Dynamometer testing comparing the pumpability performance of new and used SAE 10W-30 engine oils.