Walmart is giving a 15 cent discount on gasoline if you use their credit card and a 10 cent discount if you use a Walmart gift card. It's only in 20 states through 12/24/12. You can use this link to see if your state is included. If you aren't included but plan to travel during these months in might be helpful.
Walmart offers gas discounts in 20 states through Christmas Eve – Reuters | WalmartHelp.com
Walmart offers gas discounts in 20 states through Christmas Eve – Reuters | WalmartHelp.com