More than 50% of all drivers in the U.S. belong to a loyalty program that offers discounts on the price of a gallon of gasoline.  Unlike rewards such as airline miles or hotel points, which are aspirational and accrue over time, discounts on gasoline are a commodity-based reward and are redeemed on a regular basis. The average U.S. car owner fills up a tank more than once a week. The Fuel Rewards gasoline discount program from Excentus has 6.5 million members. They use Fuel Rewards points to receive discounts on gasoline purchased at Shell stations in the U.S. Excentus says that 85% of Ame...