The Myth of Branded Gasolines

I remember as a kid growing up in a little suburb 15 miles west of Boston, my fathers utter loyalty to Mobil gasoline. He would say that the other brands had less oomph and made the engine run improperly, I suppose he meant less octane or that the other brands were  somehow impure or inferior.
My father and most of us, including me, grew up with the illusion that different brands of gasoline are yes different; each brand came from the locations of its refinery, was refined by the refiners that drilled for it and sold at its branded stations.
Boy was I wrong. Unknown to most of us gasoline is fungible, an interesting word meaning freely exchangeable or replaceable by another of like kind or nature. What that means is that gasoline is gasoline and other than octane levels, is chemically identical to all other gasoline, no matter what brand of gasoline that you purchase. So whether you are a fan of Shell, Mobil, Hess, Chevron etc, the gasoline that you purchase at the pump is chemically identical to all of the others.
How does this work? If you happen to live in Fall River, New Bedford, Southeastern Massachusetts or Rhode Island virtually all gasoline is shipped into the Exxon Mobil terminal in East Providence, Rhode Island. However, the tankers that deliver gasoline to that terminal are not limited to Exxon Mobil, they may be from any number of different refiners, Hess, Shell, Chevron etc. that has entered into an inter- refiner agreement with the Exxon Mobil storage facility in order to increase profits.
On a given day a Shell delivery ship may arrive and on the next day an Exxon ship may arrive. The gasoline, in whatever refiners ship that happens to be delivering gasoline that day, arrives in the East Providence terminal on the ship in two tanks, one tank contains high octane gas and the second contains low octane gas. The gasoline is piped from the ship to either the high octane storage tank and mixed with whatever high octane was already present in the tank and the low octane is piped to a separate low octane storage tank. Medium range octane is gasoline is derived by simply combining the low octane and the high octane in a third tank. Its entirely probable that the gasoline in the storage tanks is a combination of gasoline from multiple refiners that arrived on different delivery ships.
The gas from the three storage tanks containing either hi test, low test or medium grade gas  is then piped to a fill station where  the various gas trucks from different gas stations arrive at the terminal to refill their trucks for their return to their individual stations
You may ask, how then do the refiners distinguish their gas from their competitors gasoline.  Simple, the re-fill pump station at the terminal, has a number of different islands, each of which is designated by the brand of gasoline that it services and the current price for that gasoline. The single pipe line from the storage tank is then split between the different pumps for each of the different gasoline brands. For example, an Exxon truck will only be filled at the Exxon pump, the Shell truck at the Shell pump etc. After the truck is filled at its designated pump, the gasoline is paid for and  approximately a quart of a  special marker is added to the tanker that identifies the fungible gas as that of that of the refiner. The gasoline is then delivered to the individual stations. If an independent gas station truck arrives, he can usually pick and choose which pump and refiners gas to buy that day, usually depending on the price.
The moral of the story is that my pop was wrong, everyone is getting the identical gasoline, whether its at an Exxon station, Shell station or a mom and pop store. Good Luck.