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Cash is king ... especially at the gas pump. I'm Kristin Arnold with your Bankrate.com Personal Finance Minute.

Everyone knows that paying cash for gas saves you at the pump. However, motorists in Orange County, California and Long Island, NY have reported that gas stations are charging consumers as much as $2 extra when they use their credit cards at the pump.

Sounds illegal, right? Well, for the most part, it is. Although retailers are encouraged to provide cash discounts, but surcharging is actually against the law. But the problem is that surcharging and discounting are vaguely defined.

In general, gas station owners pocket about 13 cents a gallon in gross profit, according to the Oil Price Information Service. Factoring in taxes, payroll and other overhead, the cost of selling gas equals 15 cents a gallon, meaning gas station owners lose 2 cents per gallon. Gas station owners claim swipe fees by Visa, MasterCard and credit cards add up to 10 cents a gallon to the price of gas. That's why some owners decide to offer a cash discount (or a credit card fee, depending on how you see it).

For more on credit cards, just visit Bankrate.com. I'm Kristin Arnold.