Amazon offers the Chevron Techron Concentrate Plus Fuel System Cleaner 12-oz. Bottle 6-Pack, model no. 67740-CASE, for $35.35. Clip the $9 off coupon underneath the item's price and it drops to $26.35 during checkout. With free shipping, that's the lowest total price we could find by $4.It's designed to clean and protect against corrosive sulfur deposits that can harm fuel gauge sensors.
Update: Note that this item is temporarily out of stock, but can still be ordered at this price for delivery when available.