You've probably had this happen to you: You see a gas station with a price that's low enough to get your attention and you drive in thinking you're saving a little compared to the stations you just passed.

Then you swipe your card at the pump and you realize you've been fooled. You go inside to the cashier to ask what's going on and they probably point to a sign the size of a postcard that says the price posted on the marquee is for cash transactions only.

Now, we've learned from well-informed sources that a prominent retail gasoline and convenience store chain in the Great Lakes region, which always had the same price for cash or credit, is announcing a 5-cent per gallon discount for April when customers pay cash. Maybe it's a pilot program. Would a cash discount determine where you'd go?

While 5-cents off is not exactly compelling, if you've got a large vehicle that takes 20 gallons or more, obviously you'll save at least a buck -- so it's not bad.

For retailers, it's easy to understand why they want to give you an incentive to pay cash. When you pay cash, the retailers can effectively reduce the fees they must pay to Visa, MasterCard and all the others. It's a significant amount that erodes their profit margins; and those margins on gasoline, believe it or not, are not nearly as healthy as the margins on beer, soda, cigarettes, candy and potato chips, etc.

Clearly, cash gets you to go inside where there's a greater likelihood that you'll pick up something and buy it, besides just paying for your gas.

At the same time, any discount on cash takes a lot of the "convenience" out of convenience stores. Customers who know they need to take advantage of anything they can to reduce their fuel budget feel compelled to pay cash when there's a discount, but, they should be aware that this may require them to drive a distance to the ATM that gives them access to their own cash without charging them for it.

The important thing is to be careful. If you're using the nearest ATM --the one at the convenience store-- that could cost you more than the amount you think you might save. And if you have to drive out of your way to get cash, or it's an inopportune time, what's the point?

Bottom line: Cash discounts on gas purchases aren't bad, but depending on the actual overall savings, they might benefit the retailer more than they benefit us.