Are they also Murphy U.S.A.? Most of the people who claim that gouging is going on, claim that there is a much higher difference than $.10 per gallon. Also another thing to think about it is why gas is more expensive at these other stations. A few gas stations such as Royal Dutch Petroleum (Shell) have a lot more additives than other stations. This would increase the price over other places such as Sams Club. Here is a site that will explain about all of that. http://www.toptiergas.com/retailers.html

In my area the biggest discount you'll get from Wal-Mart is $.05 per gallon by using their gift cards. Sure it adds up, but it isn't that much lower. Also remember that many of these stations will offer special frequent customer credit cards that they will offer a discount with so, that isn't unusual.