Originally Posted by dadto2
The base gas is all a generic commodity. Various refineries pump it into the pipeline, the pipeline dumps it at the tank farm, trucks load at the tank farm... The branded additives are mixed as the trucks are loaded. Walmart base gas is the same as Shell, Mobil, Sunoco, Marathon, Tesoro, or whatever you have in your local market. The additives are the only difference. If you aren't using Top Tier, then run a bottle of your favorite PEA cleaner every 5k. You can buy a LOT of Techron or Gumout with the money you save on the $1.25/gallon difference!
The base fuel is a commodity, and the primary distributors are pipeline operators like Plains All American, Colonial, Kinder Morgan, etc. Even for relatively short distances, it makes more sense to transport via pipeline than via truck. Longer distances may be transported by rail, although pipelines are still cheaper.
The job of the pipeline operator is kind of like a bank. Put it in here. Withdraw it there. The customer (the gas station) doesn't really care if the money that an uncle sent three states away at a bank branch is the same money that the nephew withdraws at a different bank. The pipeline operators figure out how to get X amount of fuel at a certain terminal. It may even be blended from different refineries with product that meets the requirements. I guess there is a little bit of inefficiency in the transmix unless they're willing to use pigs to prevent mixing. But the transmix is then re-refined.
In my area it's no sure thing where the fuel comes from. The closest fuel terminals to me are in Richmond, California, which has a prime location near fuel tanker docks and one refinery. There's Chevron, Kinder Morgan, Phillips 66 (their refinery is in Rodeo about 7 miles away), and TransMontaigne (acquired from Plains All American). They're constantly horse trading, especially when there are refinery accidents or planned maintenance.