Changing the oil regularly is one of the most important things you can do for your engine. If don't read any of the other ways to protect your engine (but we really hope you do) make sure to do this one. Oil keeps vital engine parts well lubricated so that they won't overheat. Your engine can't function without it and if you go too long between oil changes it can cause permanent damage to your engine over time.
Suggestions for when you should change your oil will vary, but the most recent standard for modern cars is to change the oil every 5,000 miles (8,047 kilometers) [source: Cars.com]. Some engines can go longer while some older engines may need it sooner than that. Since we're talking about proactively protecting your engine, make sure to look up what your car's manufacturer suggests for your specific vehicle's oil change interval. If you can't find your car's manual, do a quick search online to find out when it should be changed.
We can't mention changing the oil without also stressing that the oil filter needs to be replaced at the same time. The oil filter catches all the dirt and debris floating around inside of your engine and keeps the junk from circulating back through engine. With a new filter and new oil, your engine will run smoothly, and most importantly, it'll keep all the internal parts of the engine cool and well lubricated.