Posted on 6/5/2013
What does the SAE Viscosity rating on your Motoroil bottle mean? Viscosity is the oil's resistance to flow or, for the layman, an oil's speed of flow as measured through a device known as a viscometer. The thicker (higher viscosity) of an oil, the slower it will flow. You will see oil viscosity measurement in lube articles stated in kinematic (kv) and absolute (cSt) terms. These are translated into the easier to understand SAE viscosity numbers you see on an oil bottle. A W on a viscosity rating means that the oil’s viscosity has been tested at a Colder temperature. The numbers without the W are tested at 210° F or 100° C which is considered an approximation of engine operating temperature. In other words, a SAE 30 motor oil is the same viscosity as a 10w-30 or 5W-30 at 210° (100° C). The difference occurs when the viscosity is tested at a much colder temperature. For example, 5W-30 motor oil performs like a SAE 5 motor oil would perform at the cold temperature specified ... read more