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The evolution of low-temperature viscosity requirements in the Engine Oil Viscosity Classification, SAE J300, began in 1923 with the introduction of simple limits on the pour point of selected viscosity grades. Since then, low-temperature requirements have evolved into a complex specification system that includes a separate designation (i.e., the “W-grades”), laboratory “cranking” and “pumping” simulators, and complex cooling cycles to which an oil must be subjected prior to measurement. These requirements have been incorporated into SAE J300 with the objective of improving its ability to specify the oil properties necessary for good engine starting and operation at low-temperatures. The current lack of field problems related to low-temperature operation of both light- and heavy-duty vehicles provides one indication of the success with which SAE J300 meets this objective. However, the last decade has witnessed significant changes in engine design to meet more stringent emissions and fuel economy regulations. For this reason, it is time for the industry to re-evaluate the low-temperature viscosity specifications in J300 to determine if they represent the optimum values needed for modern engine designs.
low-temperature, engine oil, cranking, pumping, starting, SAE J300, viscosity
Principal Research Engineer, General Motors Research Laboratories, Warren, MI