Just wanted to get some more info on the octane of gasoline. My car says that premium fuel is "recommended" but not essential. Does anybody know how vital it is to use high octane fuel if it's recommended. I know that if a car needs high octane fuel then you'd be dumb not to put it in. I also heard that if your car just needs regular fuel, then it's a waste to use higher octance fuel. Does it have a big impact on performance or fuel economy etc.?