Oil viscosity grades like 5W-30 describe how the oil flows cold and hot. The W number is the cold (winter) rating; the second number is flow at operating temperature. This chart shows where each common grade is used.
| Grade | Typical use |
|---|---|
| 0W-20 | Modern engines; best cold start and economy |
| 5W-20 | Many late-model gasoline engines |
| 5W-30 | The most common all-around grade |
| 10W-30 | Older engines and warmer climates |
| 10W-40 | Higher-mileage engines, warm climates |
| 5W-40 | European, performance, and some diesels |
| 15W-40 | Diesel and heavy-duty service |
Lower W flows better cold. A 0W or 5W reaches the top end faster on a winter start; the hot number must match what your engine was designed for. Always use the grade and spec in your manual.
FAQ
What do the two numbers in a multi-grade oil viscosity rating mean? The first number (like the 5 in 5W-30) describes cold-start flow behavior, with a lower number flowing more easily when cold, while the second number describes viscosity at normal operating temperature, so the oil behaves like a thinner oil when cold and a thicker oil when hot.
Choose oil with How to Select Motor Oil and size a change with the Oil Capacity Chart.