LivingSocial offers a voucher for 25 cents off per gallon (20-gallon maximum) on your next two fill-ups at a participating Shell gas station for free when you sign up for Shell's Fuel Rewards program. (Existing members are not eligible for this deal. The discount applies to two fill-ups; you must dispense to the 20-gallon limit on each visit, or you forfeit any remaining savings for the other gallons.) That beats our November mention, which applied to just one fill-up, and assuming you'll buy 20 gallons per stop, that's a total savings of $10. Deal ends January 24.

Note: Signing up for Fuel Rewards gets you instant Gold Status, so even after you've redeemed the above deal, you'll continue to receive at least 5 cents off per gallon. (You can increase your savings through various actions, like linking your rewards account to a credit card or booking travel through partner sites.) Click here for more information.