Oil Viscosity Grades
Understanding SAE Ratings
Learn Oil GradesMotor oil viscosity grades like 5W-30 tell you how the oil flows at different temperatures. Understanding these ratings helps you choose the right oil for your engine and climate conditions.
Common Oil Grades
| Grade | Cold Start | Best For |
|---|---|---|
| 0W-20 | Excellent | Modern fuel-efficient engines |
| 5W-30 | Very good | Most passenger vehicles |
| 10W-40 | Good | Moderate climates, older engines |
| 15W-40 | Fair | Diesel engines, hot climates |
| 20W-50 | Poor | High-performance, racing |
Lower W numbers flow better in cold; higher second numbers maintain protection when hot.
Conclusion
Always use the viscosity grade recommended in your owner's manual. Modern engines often require thinner oils (0W-20, 5W-30) for fuel efficiency and tight tolerances. Thicker isn't always better—the wrong viscosity can reduce fuel economy and cause wear.