Franken-gas pretty much describes the majority of the fuel that's sold. Most gasoline is transported by pipeline as unsegregated deliveries. It's like depositing to a bank, where the cash that's withdrawn will not be the cash that's deposited. The fuel itself is a fungible commodity where it can come from a random delivery or possibly mixed from several deliveries of fuel of the same commodity grade. Even the big, vertically-integrated companies, unless maybe a gas station is really close to a refinery. And even then it's who cares?
It really becomes more of a logistics exercise to make sure that however much of this or that grade is available for customers. For the most part they'd prefer to move fuel as little as possible and the customer knows enough that it doesn't matter as long as it meets the commodity specs.
It's possible to get segregated deliveries of a specific fuel, but that costs extra. As much as some people want to believe that there's something super special about this or that fuel from a specific refinery, the industry frankly doesn't care.
Mostly what "brands" a fuel is the detergent additive, but even then it's possible for different fuel marketers to use the same ones. However, I suspect that Buc-ee's probably just pays for whatever generic additive is available at the fuel depot. There is no requirement that they have their own proprietary additive nor that they exceed the EPA minimum requirement.
