Who defines the viscosity ratings for engine oil?

The viscosity ratings for engine oil are defined by the Society of Automotive Engineers (SAE). The SAE developed a standardized classification system that helps identify the viscosity of engine oils under various temperature conditions, which is crucial for ensuring optimal engine performance. This classification system uses numbers and letters to denote the viscosity grades, such as SAE 5W-30, where the "W" indicates winter-grade oil designed for low-temperature performance.

This standardization allows manufacturers, mechanics, and consumers to select the appropriate oil for their vehicles, ensuring compatibility and enhancing engine protection and efficiency. The SAE's role in this area is vital since it creates uniformity in how viscous oils are rated and labeled, thus facilitating better understanding and communication among industry professionals and consumers alike.