[enslow]

I've heard a lot of people say that their cars run worse on oxygenated gas. What is does is reduce emissions, but not necessarily improve drivability. However, there's a lot more to gasoline than oxygenation (usually from ethanol). There are the detergents and other chemicals added to keep valves clean, adjust octane, etc. I'm not familiar with all the gasoline chemistry, but I do know that it's much more complicated than oxygenated vs non-oxygenated.

Many engines (lawnmower engine size...) can be damaged by the ethanol content, so landscapers sometimes have to buy premium gasoline to avoid the ethanol.

I tend to prefer Chevron because I've heard it has the best detergent package. I could be wrong, but at least I know it's good.

I hear about nitrogen enriched gasoline. I know very little about it, but my take is that if you add more nitrogen, you're giving your engine more nitrogen to burn and make more NOx, making your catalytic converter work harder. To me, nitrogen enriching seems like a bad idea, but I could be wrong.