I constantly tell people to "GOOGLE IT"
google is your friend.
The "W" in motor oil stands for
"Winter". It indicates that the oil's viscosity has been tested at colder temperatures and is suitable for use in cold weather [1].
Motor oil is classified by its viscosity, which is its resistance to flow. The "W" rating (e.g., in 5W-30 or 10W-40) is part of a Society of Automotive Engineers (SAE) grading system:
- The number before the W (e.g., 5W) indicates the oil's flow characteristics at a cold temperature. A lower number means the oil is thinner at cold temperatures, allowing for easier engine starting and faster oil circulation in winter [1].
- The number after the W (e.g., 30) indicates the oil's viscosity at normal operating temperatures (around 100°C or 212°F) [1].
Therefore, a 5W-30 oil acts like a 5-weight oil when cold (for winter conditions) and a 30-weight oil when hot [1].
Forest I was about to tell the individual that asked the question to do exactly what you said I didn't know either. My response is from Google's AI engine.
Jim