I totally agree on the refinery/distribution point. I made the same exact point in another post. However, it is the additives that distinguish one brand from another and get the brand on the
http://www.toptiergas.com list. The detergent additives can make a difference, as evidenced by the problems on this forum.
That said, I generally use BP and Mobile based on location convenience and have never had any problems with my BMWs or other vehicles.