Let me tell you a secret...
Fill up at least 8 gallons and you get a free car wash (or a soda, but why would you choose that...). DON'T choose "free car wash" on the pump screen. Print out your receipt and bring it inside. They'll hand you a second receipt with a code for the car wash. Lately the machine hasn't been working so they have an attendant standing outside, thus it's usually only open during the day.