I was talking to the guy that owns the Texaco distributorship here in the Seattle area a couple of years ago. I asked him about "cheap" gas vs. "brand name" gas. North of Seattle there are three refineries. They all pump their gas through the same pipeline (you may have heard about when it ruptured and exploded killing 3 kids a few years back) to Harbor Island in the Seattle industrial area. All the gas in the Puget Sound area comes out of that pipe. A Texaco driver pulls his truck up to the pump and slides his key card through the reader. The dispenser then fills his truck with gasoline and a proprietary additive package for Texaco. The driver for Union 76 comes next and swipes his card. He gets the Union additive package. The driver for AM/PM pulls up and gets a tank of gas laced with cat urine. And so on. It all comes from the same place, just with different stuff in it. About 8 years ago I stopped buying gas from AM/PM and other discount places and switched to Union 76. I didn't notice any increase in power, but I did start getting better mileage immediately. It's all in the additives.