ASTM Committee D-2 has undertaken a program to develop a laboratory test which correlates with low-temperature engine oil pumpability in field service. As the first step in this program, pumpability data were obtained using thirteen ASTM Pumpability Reference Oils in seven full-scale engines. The engines and oils were chosen to be representative of a wide range of commercial practice. Borderline pumping conditions, as defined by the ASTM Task Force, were determined for each oil-engine combination investigated. The mode of pumping failure in the engines and the times required to lubricate the rocker arms were also obtained.The results indicate that substantial differences in pumpability exist among both engines and oils. Possible reasons for these differences are suggested, based on engine oil pump inlet system characteristics and the viscometric properties of the oils.The full-scale engine pumpability data should provide the basis for the development of a laboratory bench test which will satisfactorily predict an engine oil's low-temperature pumpability characteristics in service.ASTM Committee D-2 has undertaken a program to develop a laboratory test which correlates with low-temperature engine oil pumpability in field service. As the first step in this program, pumpability data were obtained using thirteen ASTM Pumpability Reference Oils in seven full-scale engines. The engines and oils were chosen to be representative of a wide range of commercial practice. Borderline pumping conditions, as defined by the ASTM Task Force, were determined for each oil-engine combination investigated. The mode of pumping failure in the engines and the times required to lubricate the rocker arms were also obtained.The results indicate that substantial differences in pumpability exist among both engines and oils. Possible reasons for these differences are suggested, based on engine oil pump inlet system characteristics and the viscometric properties of the oils.The full-scale engine pumpability data should provide the basis for the development of a laboratory bench test which will satisfactorily predict an engine oil's low-temperature pumpability characteristics in service.