My point Vizzy is to not make a blanket statement everywhere.
When I am in Northern MN, pretty much I am getting the same gas everywhere.
When I am in the Twin Cities, I can procure gas from Holiday and know it was refined at Flint Hills, gas from Superamerica was refined in Saint Paul Park, and it used to be that BP/Amoco gas was refined in Mandan, ND, but that refinery, pipeline, and terminal was all sold, so who knows where its from now.
If you do a little research, you can learn a lot about who supplies what in you area, and in SOME cases, it may be about the same at every stations, other not so.
Buyer beware...