I use the one at Eagle Stop on Battlefield. Buying a wash when you fill up will lower gas by $0.20 per gallon. The wash price range is from $5 or $6 up to $10. I get the $8 wash, so it's costing me around $5.50-ish when factoring in the fuel discount. I don't know exactly how this compares to other touchless car washes in town, but I think it's probably a little less expensive than most when considering the discount on gas. FWIW, this station is unfortunately a big hangout spot for motorcycle douchebags.

Other options in town that I've never used are Patriot Auto Wash and Auto Spa.