I guess I don't get too worked up about gas prices/gas price advertising. Let's be honest, they have everything right there on the sign. They are capitalizing on the fact that many people do not bother to read the complete display. And, people rarely check to see if the price that it shown on the pump is the same price as shown on the board.
Either way, people will go out of their way to avoid paying $0.04 per gallon, which makes very little sense to me. Most people drive vehicles with a 16 gallon tank. So, they normally buy probably 12 - 14 gallons per fill up. And, maybe you fill up once per week (obviously, those who drive more, fill up more often). Buying 14 gallons of gas at a $0.04 per gallon premium costs you an additional $0.56 to fill up. Filling up once per week - $2.24 per month or about $27/year. When you consider what it costs you to drive your car (the IRS says $0.55 per mile - most people say $0.25-$0.30 per mile), that means that if you go more than one mile (each way) out of your way to save $0.04 per gallon, you will spend more money driving for the cheaper gas than you will save buying the cheaper gas. Which means that if you live in South, and drive past the Texaco to HEB or even Murphy (Wal-Mart), and don't save at least $0.04 per gallon, you have spent more money than you save. And if you drive by Texaco to get to HEB and save $0.08 per gallon, you still have only saved a net of $0.50!
I drive an F-150 with a 28 gallon tank. What I do is when the tank gets to about a quarter full, I kind of keep track in my mind where the cheap gas is - HEB, Wal-Mart, Raceway, etc. - and, when I go by one of these places, I just pull in and fill up. May not be empty but I top off with cheap gas.