Evaluation of Laboratory Viscometers for Predicting the Cranking Characteristics of Engine Oils at 0 F and −20 F - (Report of the Group on Relationship Between Oil Characteristics and Engine Cranking of the Motor Vehicle Fuel, Lubricant, and Equipment Research Committee of the Coordinating Research Council, Inc.)

A study of the correlation between engine cranking data and viscometric data at 0 F and -20 F has been made by the Coordinating Research Council. Two laboratory viscometers, the Cold-Cranking Simulator (CCS) and the Reciprocating Vijcometer (RV), have been found suitable for predicting the engine cranking performance of oils at 0 F and -20 F. Data from ASTM cooperative programs with these two instrument types agreed and both showed good correlation with data from CRC engine cranking programs conducted at 0 F and -20 F. The CCS had better repeatability than the RV at 0 F, but both viscometer types were equivalent in this respect at -20 F. Although the cone-plate viscometers gave the best correlation with engine cranking data at 0 F, they failed to provide the desired degree of precision in a second ASTM program at this same temperature; hence, no cooperative data were obtained at -20 F. The CCS and RV instruments, as the engines, showed that low-temperature viscosity should be determined at the temperature of interest and not inferred from measurement at some other temperature.