Distributor owns most, of the stations and sets the prices.This is the reason everyone in our area is at the same price and same situation in Indiana and Michigan after Shell bought out the other Distributor many years ago.
They do price according to what someone else who owns stations might be competing with. One exit has a Pilot and it set the price and everyone else follows. It is cheaper down the road a bit.
One of the stations is only open for a few months sometimes. They get some to operate it and charge say 6,000.00 a month on the lease. the station might only clear before paying themselves 8,000.00. so they close up. Try to set the price at something lower to get traffic and Distributor won't deliver gas.
Additives are added when they load the fuel at the tank farm. Label on truck doesn't mean anything.
Pilot stations generally use their own trucks but load at the same tank farm.
All Distributors get their fuel from the only tank farm here now. Use to be three Operators. More and more Low cost Distributor owned stations/convenience stores don't put in any additives. I add the Chevron stuff from WalMart.
Some Shell gas advertised as tier two or three or whatever, 93 octane makes the engine ping, in our little car. They lead you to believe there is no ethanol, in the premium, but there is, unless they advertise it does not.
There are three stations, right here, that sell no ethanol gas, no additives, and they charge a lot more, for fuel, that cost a lot less but isn't with subsidized ethanol.
Exxon Distributor but most of the stations sell ethanol blend.
Exxon label, on a Convenience Market, usually means Exxon owns it, now, but it is the same gas as everyone else except with the specified additives, if any by Exxon loaded on the tanker at the tank farm.
Each Distributor buys fuel form the same tank farm. Deliveries to tanks of 87 octane, and 89 and 93, in this area are in the lines from ports and refineries in slugs.
Obviously even with the pigs there is some mixing and the real octane is variable. this is the reason Cars now have knock sensors and so on and reprogram engine operating paramaters in computers, and why your car may run like s--- in some parts of the Country from the same brand and octane.
None of it is really 93 octane. A load of lead free acing gas 104 octane or even 98 octane and the little car comes on like gangbusters, after computer adjusts.