Sunoco i found was one that had a different motor octane rating and alot of people get confused when buying VP fuel due to the fact when they see C12 they beleive its 112 octane awnser is no its 108 motor octane and its good up to a 15:1 c.r. motor. C16 they beleive is 116 octane, the awnser is no its 117 motor octane. I sold race fuel for years and ran into this problem weekly. I advise everyone read the fine print when buying your fuel.