Something I never thought much about before but is completely obvious...
The Colonial pipeline carries about half of the gasoline used by the east coast of the US. There are tubes for different grades of gasoline There's a tube for gas and a tube for diesel, kerosene, etc., but there are not separate tubes for each brand and each of that brand's grades. So, gas is gas. Doesn't matter which station you go to, odds are good it's the same stuff across the street.
In some respects, that’s true, however each brand has additives/alcohol/blends that they formulate at the rack. When the fuel comes off the pipeline, it’s delivered into bulk tankage. That fuel then gets specialty additives when it goes from bulk storage into the transport truck that delivers to the station. So, while the base product is identical, the end product is different.
Also, I may be wrong about the Colonial Line, but most pipelines are single pipes not multiple lines. So they run a “load” of diesel fuel through the same line they run gasoline, Jet A, Kerosene, et c. They run a “pig” through the line between loads that cleans the pipeline, preventing most cross contamination.
Colonial has two tubes. one for gas and one for the other stuff.