My mileage is alright. I can usually get 500 k out of a tank of gas. Definately less if I drive too fast though. I do use injector cleaner every oil change which for me is about every two months. Other than that I use decent quality gas. I don't use Sunoco Gold as I seem to get worse mileage with it. 91 works well. I avoid Esso as it is one of the dirtest fuels on the market.
I dont really do much else other than the regular maintenance stuff.
