Gasoline does not come from "all the same places."

MI is served by two crude oil pipelines and several refined product pipeline, which bring gasoline from several refineries.

Most gasoline comes from the Exxon-Mobil refinery in Joliet, IL and the BP refinery in Whiting, IN. Although all the gasoline goes through the same pipeline, the E-M products are separated from the BP gas by "pigs" which isolate the products from each other. Each refinery formulates its gasoline somewhat differently depending of the grade of crude from which it's refined, the weather and other factors. Gasoline from those two refineries are sold through jobbers to many differently branded stations.

We also get a lot of product from the BP Toledo refinery.

MI's one refinery, Marathon, receives crude from Canada and a couple other pipelines. It's gas is also sold through jobbers to many differently branded stations.

MI and Detroit gave millions of our tax dollars to Marathon several years ago to induce it to expand its refinery to crack Canadian [[low quality) crude oil. It was not necessary to do that. I recall Marathon spent $7 billion to acquire a 20% interest in many thousands of acres of Canadian tar sands leases in order to gain access to that source. It then had to decide whether to build a new refinery in Canada to refine its crude or move the crude to Detroit for refining. It was a no-brainer as it was far less expensive to expand its Detroit refinery to be able to refine the low grade crude than to build a new refinery in Canada. So, it would have done what it did without any tax incentives, which we just pissed away.