Synthetic Oil Explained Whether it's evil stuff or good stuff depends on who you talk to. And a lot of what you hear from backyard mechanics are rumors and myths. Myth # 1 The claim that you don't have to change Synthetic oil as often as regular motor oil. Remember when Mobil 1 said you could go 25,000 miles between oil changes with synthetic oil? Notice they haven't said that for a good number of years? Keep that thought on the back burner for now... Myth #2 That synthetic oil causes oil leaks. In this article I'm going to try to dispell these myths for you with the cold hard facts about the differences and similarities between mineral vs. synthetic oil. Let's talk first about what "mineral" oil. Mineral oil is created from something called "Base Stock". Base stock what the oil companies get after they have processed the crude oil that comes from the ground. From there, additives are combined with the Base Stock, to create our motor oil.