It is all branding, just like the Ford vs. Chevy vs. Dodge vs. Tundra and so on, it is a known quality good or bad depending on how you feel. I burn Shell because it is close to my home and it also runs good in my sports cars and my boat. On the road I stick with brand names just because I hope someone from Shell or Exxon takes a look at the stations and equipment so that I know it is safe and not full of water.
To the guys who do the hauling, with all the piping I see on the tankers I have to think they are divided into separate tanks so different grades and qualities can be carried in the same truck at the same time.