* 5W: This refers to the oil's viscosity (thickness) at low temperatures. The "W" stands for "winter." The "5" indicates that the oil flows freely at temperatures as low as -25°C (-13°F). A lower number means better cold-weather performance.
* 20: This refers to the oil's viscosity at high temperatures. The "20" indicates a relatively low viscosity at operating temperature. This means less internal friction and better fuel economy, but potentially less protection at extremely high temperatures or under heavy loads compared to higher numbers.
In short, 5W-20 is a relatively thin oil designed for good fuel economy and cold-weather performance. It's commonly used in modern gasoline engines, especially smaller ones. However, always consult your vehicle's owner's manual to ensure it's the correct oil for your specific car. Using the wrong oil viscosity can damage your engine.
