We have several that offer 3 cent discount for cash. Generally we don't have to pay ahead of time unless the station is close to the interstate.
I will say this, the stations make their money off of instore convenience items, they don't make much off the gas fuel sales. Cash discount is a great way to entice customers to come in and see that maple frosted donut
I buy Exxon or Shell gas from high volume stations. I don't have a Costco near me and I'm not going to buy the cheap stuff to save a penny or two per gallon.
I have a BP that matches it's prices with what's around the area. Top Tier. you get .01 cent for every 10 dollars spent, even if you use your rewards for that transaction. There's always someone there and I caught the town inspector one time who said their pumps are always accurate. Kinda funny seeing him carry those gallon measuring pails with a stick sticking out in the middle.