Here's the breakdown:
* 15W indicates the oil's viscosity (thickness) at low temperatures. The lower the number, the thinner the oil. So, 15W is suitable for cold temperatures.
* 40 indicates the oil's viscosity at high temperatures. The higher the number, the thicker the oil. So, 40 is suitable for hot temperatures.
Therefore, 15W40 represents a multi-grade oil designed to perform well in a wide range of temperatures. It is relatively thick at low temperatures and thins out at high temperatures, providing adequate lubrication in both conditions.
This type of oil is commonly used in various gasoline and diesel engines.
