I live 8 miles from one of Marathon's largest refineries. I have nothing good to say about Marathon. I've heard that they have the absolute minimum detergency requirement (as required by the gov't.) When Marathon bought out Ashland oil many years ago the price fixing started in my region. We've been getting screwed severely for the last 10-15 years. I know gas has been expensive everywhere, but we have been particularly hard hit by Marathon's virtual monopoly in my area. Murphy USA went in about a year ago and has broken the Marathon Gas Price Cabal in one small area. Also, when Marathon took control of Ashland Oil and their retail stations, the price of a bottle of Pepsi or Coke instantly increased exactly 20%. THAT is just a stark indicator of the company's attitude and intent.
Oh, and the fuel IS bottom of the barrel quality in terms of additives.