SAE stands for the Society of Automotive Engineers. They’re the clever folks who decided we needed a universal standard, so mechanics wouldn’t just guess and pour maple syrup into your car. Their rating system is basically a secret handshake for oils.
The “W” stands for “Winter,” not “weight,” as some people assume. The number before the W tells you how the oil behaves when it’s freezing cold. The number after the W tells you how it behaves when your engine is hot enough to fry an egg on the hood.
