The “W” in an SAE 5W-30 stands for Winter. The “xW” represents the low-temperature characteristics of an oil, while the non-W grade represents the viscosity at operating temperatures. The lower the W-grade, the better the oil pumps and flows at cold temperatures. The “W” grades are defined by the Cold Crank Simulator (CCS) and Mini-Rotary Viscometric (MRV) test. The Cold Crank test is used to determine if the oil will allow the crankshaft to turn over fast enough for the engine to start. The Mini-Rotary test measures the pumpability of the oil at low temperatures.
Better than it has to be®. . . Since 1903
