I had a friend in high-school who would buy gasoline from the same gas station every week. He filled it up at a Texcoco gas station and used a discount card to fill it up for 10 cent less per gallon. Gas companies utilize discount cards to build customer loyalty by giving a miniscule discount of 2 to 3 percent (5 to 10 cent off). This makes a person volatile to shop at that location only, and miss out on the other locations that they are not a member of. Since most gas stations where I live are not branded, it closes the oppurtunities they have in shopping around for gas, by making one option slightly cheaper in a manner that is perceived greater than it really is.