Just as a curiosity do you know where the Chevron fuel you are buying is coming from? I work at the Citgo Refinery here in Lake Charles, Louisiana; there is also a Conoco refinery here in town, where do you think all fo the Chevron, Shell, Texaco, and etc. gas stations in town get their fuel from? Do you think they truck in into town from their nearest refinery, that's probably two states away? Hardly seems cost effective does'nt it? All Gas is the same minus the addative/detergents. What ever gas you are buying is probably coming from the nearest refinery/pipeline, they only thing you get when you buy a certain name brand fuel is that company's addatives/detergents.
The only other thing that I'll touch on is some refineries still produce 100% gas, not gas with 10% ethanol. I have noticed that if I buy 100% gas, I get noticably better fuel economy, that is because the 10% ethanol that is in other fuels, burns slower and decreases your fuel economy.