When it costs nearly $50 to fill up an average car’s gas tank, few people want to hear that the guy who owns the gas station might not be making any money.

But industry officials and local gas station operators said that’s just the case. Gas stations earn just pennies for every gallon of gas purchased, they say, and if a motorist pays for the fuel with a credit card, that eats into profit even more.

Randy Black, who owns five Mega Star gas stations in North Georgia near the Tennessee state line, said he buys his gas for about $3.45 a gallon and was selling it for $3.49 Monday.

That’s still a profit “but if you use a credit card, and a great majority do, credit-card companies takes 2.5 percent and that adds up to about 9 cents a gallon that goes to the credit card companies,” Mr. Black said. Which adds up to Mr. Black losing about 4 cents a gallon if a customer pays with plastic, he said.

“I don’t want to hear all that,” said Joshua Pritchard, a Knoxville man who drove his Ford Expedition to Chattanooga for a job interview this week. “I drive a big gas guzzler, so it literally empties my bank account every time I go to the gas station. If they charged enough to make a profit, I’d have to decide between food and gas.”

Gasoline prices shot higher at the pump Wednesday, rising more than 2 cents overnight to a national average of $3.53 a gallon with prices expected to push to $4.20 by summer’s end, according to AAA, the Associated Press reported.

Lower profits are being felt not only by small retailers like Mr. Black, but by the big gas sellers who operate thousands of stores, said Jeff Lenard, spokesman for the National Association of Convenience Stores.

Convenience store industry sales reached a new high of $577.4 billion in 2007, but profits dropped by $1.4 billion, largely because of higher credit-card fees, Mr. Lenard said.

Surveys show many consumers believe retailers keep about 60 cents on every gallon of gas sold, Mr. Lenard said, when in fact industry figures suggest that, at the very most, retailers take 13 cents, and on average they keep about 8 cents a gallon, he said.

Industry officials say pump maintenance and electricity absorb some of that profit.

Because convenience stores know how tight the market it, they try to lure consumers from the pumps to the stores, Mr. Lenard said.

MapCo, a Brentwood, Tenn., convenience store operator with 496 stores in the Southeast, is changing its approach — adding low-calorie snack foods, vitamin-enriched beverages, specialty candy and providing brighter and bigger stores that feature full-service restaurants in some locations, said Paul Pierce, the company’s vice president of marketing.

“Traditionally our business has relied on single men, 18 to 35 years old, working-class, blue-collar guys,” Mr. Pierce said. “That’s still a good market for us, but we’ve got to go after other customers, too.”

MapCo operates two chains of stores in the Chattanooga area: Favorite Markets and Fast stores. Fifty of those locations will get makeovers in the next few months, re-branded as MapCo Markets, Mr. Pierce said. Those changes include bright-green exterior signs and improved offerings on the stores’ shelves. A new store being built in East Ridge near Interstate 75 will include a full-service restaurant called GrilleMarx, Mr. Pierce said.

Selling food is one of the best ways convenience stores can increase profitability, Mr. Lenard said. But it’s an expensive proposition for the smaller stores such as Mr. Black’s.

“I’ve just got to cut costs and make money where I can,” Mr. Black said.

Complaining to customers or friends isn’t going to help, however.

“We don’t get any sympathy,” Mr. Black concedes. “All people care about is how much it’s costing them.”

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