Yesterday while I was driving for a few minutes from my friends house my focus decided to start sputtering like it was misfiring then all of a sudden my check engine light comes on. Later in the day my friends tells me he put octane boost in my car without telling me and I want to know the jeist of how bad the damage is. It puffs small amount of white smoke coming out of the exhaust. It's not overheavint. No milk substance on the oil cap and no air bubble in the radiator fluid..