This is an important question to ask! In general, it’s not recommended to use 5W-30 oil (or any other motor oil weight) in place of 5W-20 oil, as the difference in viscosity has the potential to damage your engine.
Ultimately, the difference between 5W-20 oil and 5W-30 oil comes down to their viscosity, or thickness—particularly once the engine reaches normal operating temperature.
5W-20 oil and 5W-30 oil have the same “winter rating,” meaning they exhibit the same viscosity in cold weather (that’s what the “W” stands for). But when exposed to high temperatures, 5W-30 oil stays a little thicker.
When your engine runs for a few minutes and reaches an operating temperature of 212℉, 5W-20 oil will be much thinner and flow with more ease than 5W-30 oil, which remains thicker and flows with more resistance.
It’s never recommended to use an oil weight different from the one recommended by your owner’s manual. Filling your engine with the right oil helps keep it working at peak efficiency.