Gasoline is a fungible commodity. Several different refineries pump base gasoline into a pipeline. They pump in hundreds of thousands of gallons of 87, then 92, then various fuel oils, etc. Along the pipeline are terminals with tank farms. The terminals pull out the 87, the 92, etc. and pump into the tanks. Everything at the tank farms is potentially produced by several refiners. (the 87 tank is all 87, but could have Sunoco, Hess, Valero, and United Refining mixed in it, depending upon who is connected to that pipeline.
When a delivery truck pulls up to be filled, his orders stipulate X gallons of Sunoco in one compartment, Y gallons of Mobil in the next compartment, Z gallons of unbranded in another compartment, etc. The terminal operator blends the additives unique to each compartment as he fills them.
Then the trucker delivers to the Sunoco station, the Mobil station, the 7-11, and so on.
Unbranded is not less expensive because it's old, or watered down, or whatever. It's all market driven. Mobil and Shell are more expensive because their marketing campaigns have convinced a segment of the market that their gas is better. BJs, 7-11 and the local "generic" brands sell to customers who buy on price. BJs doesn't pay a royalty to Mobil on each gallon they sell, so they don't have that cost.
When a delivery truck pulls up to be filled, his orders stipulate X gallons of Sunoco in one compartment, Y gallons of Mobil in the next compartment, Z gallons of unbranded in another compartment, etc. The terminal operator blends the additives unique to each compartment as he fills them.
Then the trucker delivers to the Sunoco station, the Mobil station, the 7-11, and so on.
Unbranded is not less expensive because it's old, or watered down, or whatever. It's all market driven. Mobil and Shell are more expensive because their marketing campaigns have convinced a segment of the market that their gas is better. BJs, 7-11 and the local "generic" brands sell to customers who buy on price. BJs doesn't pay a royalty to Mobil on each gallon they sell, so they don't have that cost.