Right now at Groupon, you can pre-pay for $80 worth of gas for $52: that's a 35% discount on the price of gas. To sweeten the deal, Ebates is offering 9% back on deals at Groupon today, saving you another $4.68. Since Winn-Dixie (and some other supermarkets) gives a 4% rebate towards Shell gas when you purchase a gift card, I bought Groupon gift cards there first. This saved me another $2.08. I also receive 5 Hilton Honors points for every $1 I spend on my American Express, so each deal (I bought 8 deals) earned me 260 Hilton Honors points.
Bottom Line: for $80 in gas, I paid $45.24 and received 260 HHonors Points
Note: The gas is rewarded as $1 off per gallon up to 20 gallons. I use gas cans when I fill up to guarantee I get the full benefit of this offer. ETA: After calling Fuel Rewards, the cards were added to my account in such a way that I am not limited to just redeeming $1 per 20 gallons. I can stack these cards, so if gas costs $2/gallon, I can redeem $2 off per gallon for up to 20 gallons.