SVM Gift Cards via eBay is offering a couple of decent gas card discount deals. Currently you can purchase $100 BP or Exxon Mobil gift cards for $95. There is a limit of 3 of each type of card per user id.
Purchasing these cards should earn you 2% back in eBay Bucks and another 2% through a portal. You may also be able to use the discounted eBay gift card deal to save even further, however keep in mind that eBay gift cards take up to 4 hours to activate. In the past these gas card deals have normally lasted a few days, but that can always change.