Amazon offers Prime members the Gumout All-In-One Fuel System Cleaner 10-oz. Bottle 12-Pack, model no. 800001366, for $13.77 with free shipping. (Non-members can spend $49 or more to qualify for free shipping; otherwise, shipping costs $8.97.) That's about $1.15 per bottle and about $75 less than what you'd expect to pay at your local store for a 12-pack. (For further comparison, we last saw a single bottle for $6 in December.) It purports to fight corrosion and improve fuel system performance.

Note: This item is currently on back order, but you can order it now at this price and it will ship when available (which is estimated at approximately three to five weeks).