BOSTON (TheStreet) -- Fill up your car at supermarkets or wholesale clubs that sell gas and you'll enjoy some high-octane savings -- as much as 14 cents a gallon on average over what competitors charge, a study by market tracker GasBuddy.com shows.
"You might not save 10 cents a gallon every day, but you'll find good deals a majority of the time at the outlets we've identified as being the most competitive," says Patrick DeHaan of GasBuddy, which analyzed a year's worth of daily pricing at 120,000 U.S. gas stations to determine which chains offer the best deals.
Grocery stores and wholesale clubs account for seven of the 10 chains that the firm found offer the lowest average pump prices among retailers with 50 gas stations or more.
DeHaan speculates that the winning chains sell gas for little profit -- or even a loss -- just to get customers into the door to buy other things.
"If folks stop in to buy gas and say: 'Hey, I'm going to go into the store and spend some money on other things as long as I'm here,' that's where the chains make their money," he says.
And even though joining a wholesale club costs around $50 a year, DeHaan says many drivers will find the investment well worth it.
"I would say that if you drive more than 15,000 miles a year and plan on filling up at [a wholesale club] at least 50% or 75% of the time, your gas savings can certainly offset your membership fee," he says.