Let me begin by saying that I am all for gas stations charging less money for fuel purchased with cash. As a consumer I have the choice of the convenience of the credit card or the economy of the cash transaction.
The Marathon gas station nearest the house can have $0.15/gallon price-swings overnight. In either direction. About a mile north, there's another Marathon station and a BP station. And they are *always* not-more-expensive than the one nearest the house. (And as a consumer I can choose to go out of my way for a probable economy or stop on my way home for the convenience.)
On the way to work this morning I had "light". $4.099 at the nearby Marathon. I decided I'd check out the pair north of the highway. When I looked at the signs (they're "always" the same price) I saw $4.059. Cool. I pulled into the BP, because, regardless of politics, that one is the best situated for pulling out of. I parked at a pump, fed in my credit card, went to push the button on the left, saw $4.139. Wondered if they had moved the cheap gas to a different pump, but that was
the cheapest gas. Looked at the sign. $4.059 = CASH price, $4.139 is credit. Looked at the Marathon across the street. Their sign just said $4.059, so I hit cancel on the pump, drove across the street, used my credit card, and paid $4.059.
Heard about trouble on the freeway, so I took Washtenaw in. There are 2 BP stations within a block of each other, one of which is "always" cheaper (sometimes by more than a dime) than the other. The cheap one was $3.999. Oh well. It was on the wrong side of the street anyhow.
The Marathon at Arborland, which has a "Cash" price that is usually pretty darned good was charging $4.099.