Not that most folks will likely ever visit Fairmont, but for those who might this could be of some interest.
Most people arrive in or at least at Fairmont via Highway 15 from the North or via I-90. The big obvious place with a huge sign is Super America. This is generally the place to avoid. It usually will be a few cents a gallon more expensive than every other station town. They seem to count on folks from I-90 seeing them and figuring that everyone here charges as much as they do.
North of the Super America is McDonald's and then a Cenex station. This Cenex station will either be charging the typical Fairmont gas price or might have it a bit lower as they occasionally raise their prices a little later than other stations. The Cenex station has one other advantage, at least for local folks. The two supermarkets in town, County Market and Hy-Vee, have coupons on the back the receipts. One of the coupons is for a 5 cent per gallon discount on gasoline at that Cenex (and the one in Truman), for up to 50 gallons.
If the local gas price has just gone up, the Cenex isn't always the last station to raise its prices. There's a little station just north of the Hardee's that is occasionally the last to raise prices.
There is a Conoco station, also on Hwy 15 in town, that promotes itself with a gift for a 10 gallon fill (if I recall correctly). The gift is either a candy bar or a can of pop depending on the season.
There is a downside to the Cenex, the station by Hardee's, and the Conoco if you prefer to use a card for gasoline. None of those stations are set up for pay-at-the-pump.
After that, there's really no other difference for folks just visiting Fairmont. I have been told that a Freedom station on Blue Earth Avenue has a punch card thing set up. I'm not sure how much it takes to get a single punch in the card, but when the card is fully punched (eight punches, I am told) then it can be used to get a "free" car wash at the station's wash. I've never tried the car wash there, punched card or otherwise.