Marathon came to town here last year. I tried a few tanks of their gas, it did OK. Then one day I got a tank of gas that did not do so well, my truck did not run very well after that fill-up. I ran about half of it out and topped up with 7-11 gas and it did better, so I kept using 7-11 until now.
Just a couple weeks ago I decided to give Marathon another try and bought a tank of their gas. So far my truck is running great, seems to have a little more power and pep than it did on 7-11 brand gas, but that may be placebo effect. I do know the throttle responded very well the other day when I had to gun the engine to get away from another driver on the road that was too close for my comfort.
Marathon is an American company based in Findlay, Ohio. Last year they separated from Marathon Oil and became a stand-alone company. 70% of the oil they refine is from the USA, Canada or Mexico. Marathon Petroleum does not drill for oil, they only refine oil into gasoline. They employ about 1600 workers in Findlay plus they have workers at their refineries in several states here at home. Marathon does not post the obscene quarterly and yearly record profits that we see from the major oil companies. That is a good reason to buy Marathon gas. I would rather not add to the multiple billions of dollars of profits at Shell, Chevron, etc.
As long as I can get good performance from Marathon gas I will continue to buy it because I am happy to help keep American workers employed and help an American company turn a profit.
One thing I wonder about, is 7-11 and cheaper stations maybe get their gas from the cheapest supplier they can find. Marathon is in the business of refining and blending gas, and maybe their gas and add pack is better than 7-11 or the mom and pop stations? I don't know. Marathon touts their "STP Additives" but that is just a brand name they put on their add pack, it is not really made by STP and is not the same as the STP fuel add you can buy at Walmart.
I have also read that Speedway is the same as Marathon, I know Marathon owns Seedway but Speedway is always cheaper than Marathon. I have to wonder if Speedway has a lesser quality add pack, but we have no Speedways here so I really don't worry about it much. Marathon seems to be pretty good gas.