Gasoline at $4 a gallon might be a burden for consumers, but it is a windfall for credit card companies, according to industry experts.

Caught in the middle are the gas station operators, who must pass the credit card fees on to their anguished and angry customers.

The profits enjoyed by the credit card companies are from hidden fees they charge retailers, according to Ross DiBono, executive director of the 650-member Pennsylvania Association of Gasoline Retailers and Allied Trades.

So, retailers say, don't blame us, blame the credit card companies.

"We're still selling gasoline for only 8 to 12 cents more per gallon than we pay for it - the same margin as 15 years ago," DiBono said.

Credit card fees are based on a percentage of the total sale. That ranges, depending on the brand of credit card, from 1.6 to 2 percent.

On top of that, DiBono said, there is a credit card transaction fee of about 10 cents.

So a 20-gallon fill-up, at $4 a gallon, costs $80. At that rate, as much as 8 cents a gallon is going to the credit card company and to cover oil company costs of processing credit card transactions.

The profit margin of 8 to 12 cents per gallon charged by station operators has to pay the people who work for them, the rent or mortgage, and the electric bill.

Why not just raise prices? Retailers such as Wawa, which sell gasoline as a sideline, set the market price. "Get more than 1 or 2 cents over their price," DiBono said, "and you get hurt."

Trade associations urge retailers to offer discounts for cash purchases to show customers what credit card companies are charging. But retailers say they are not expecting that to go far. Among other things, many major oil companies prohibit the practice because already-angry customers do not like paying the penalty.

Priscilla McDonald, for example, became annoyed yesterday when she saw a 10-cent discount for cash at the Xpress Gas station at South Columbus Boulevard and Tasker Street. "I'm moving on," she said. "I'm not paying 10 cents more. I don't carry cash."

But credit card use for buying gasoline is soaring. DiBono and others estimate that more than 75 percent of gasoline is now bought with credit cards, a 25 percent increase over a few years ago.

With fill-ups sometimes costing more than $75, "cash purchases are less and less every day, particularly among women and seniors, who do not want to risk carrying that kind of money," said Kirk McCauley of the gasoline retailers trade association in the Washington-Baltimore area.

The retailer can avoid the fee if customers use their bank ATM cards to buy gasoline - if the pump is equipped with a keypad on which they can enter their PIN. And if the customer remembers to tap "debit" when asked what kind of card he or she is using.

Retailers also get a break if the customer uses the credit card issued by the oil company whose products they sell.

But debit and oil-company credit cards are only a small percentage of credit card purchases. More and more people are lured to MasterCard, Visa and American Express to get bonus points that can be exchanged for gifts or travel later, DiBono said.

Several credit card companies declined to discuss the situation yesterday.

Sunoco Inc. said it had been working on the problem for 18 months. "We have been talking to the major credit card issuers and explaining how their fees and policies are not friendly to the gasoline retail industry," spokesman Thomas P. Golembeski said.

"We are trying to get them to change how they work," he added.

Any progress?

"None that we can talk about," Golembeski said.

Contact staff writer Henry J. Holcomb at 215-854-2614 or hholcomb@phillynews.com.