Often an exercise of maintenance that is overlooked, changing your oil is one of the easiest and cheapest ways to make sure that your engine and car stays in good shape. There's no need to be going in to Jiffy Lube every time, either. This is something you should be doing on your own. Now, the age-old saying is to change your oil every 3,000 miles. Although this won't hurt your car, it's not exactly necessary, especially with new cars. Typically, 4,000-6,000 is still an acceptable range to keep your oil churning, and you can even go with the extended-range oils for 10,000 miles, if you don't care about your warranty. However, just in case, it's always good to write down a schedule and watch for signs that your oil is bad. What are those signs you ask? Take a look.