LOW-TEMPERATURE PUMPABILITY CHARACTERISTICS OF ENGINE OILS IN FULL-SCALE ENGINES.

Borderline Pumping Temperatures based on gallery oil pressure traces were determined for all thirteen Reference Oils in four of the test engines, and for nine of the Reference Oils in all seven test engines. Data were also obtained as to the type of flow failure occurring (air-binding or flow-limited) and on rocker arm oiling times. The results indicate substantial differences in pumpability among both test oils and test engines. Possible reasons for these differences are analyzed, and a model, based on engine oil pump inlet system dimensions, is proposed. This model accounts for some of the differences found in engine severity and the type of flow failure which occurs. The pumpability data reported should provide the basis for development of a laboratory bench test to predict engine oil pumpability.