Aww come on guys, I like a good debate! If you disagree with what I say please, pick it apart and show me which one you disagree with! haha
Buuut lemme try this again:
The reason you may get better mileage with premium is because you'll lose power with lower octane fuel. The lower power requires you to press the gas pedal harder for you to get the same acceleration feel hence you burn more. This isn't the engine acting, its your foot.
The misconception about higher octane being cleaner is just that, a misconception. All octane ratings, no matter what the brand, contain cleaning detergents to protect against carbon buildup. This is actually mandated by the EPA.
If you want more info read: http://chemistry.about.com/cs/howthi.../aa070401a.htm
It gets complicated at times but its good info. So to quote me
DrJay says: "Using lower octane does not necessarily give you better gas mileage and is not bad for your supercharged engine. It also does not cause more carbon buildup. It is, however, bad for performance."
I wanna debate though