What does the "W" in 10W-30 represent?

The "W" in 10W-30 stands for "Winter." This designation indicates the oil's viscosity rating in cold temperatures. The first number, "10," represents how the oil flows at low temperatures, while the "W" signifies that this measurement is taken in winter conditions. Thus, a lower number means that the oil is less viscous and can flow more easily at lower temperatures, which is essential for engine start-up in colder weather. This characteristic is critical for ensuring proper lubrication and protection for the engine during those cold starts.

The second number, "30," refers to the oil's viscosity at higher operating temperatures, indicating that it will perform consistently under normal engine operating conditions. This dual rating is important for understanding the oil's performance across different temperatures, ensuring that engines run smoothly throughout varying climatic conditions.

Understanding this rating helps engine owners select the right type of oil that will provide optimal protection and performance for their engines, especially in regions that experience cold winters.