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.
Read on to see which chains offer drivers the best average prices when compared with nearby competitors.
GasBuddy based the rankings below on how much outlets charged for unleaded regular gasoline on each day last year vs. what competing stations in the same ZIP code asked for the same grade of gas on the same date.
The top 10 chains are:
10. Stop & Shop (average savings: 5.7 cents per gallon): Owned by Dutch retail giant <B<Ahold, Stop & Shop operates some 400 grocery stores in New England, New York and New Jersey -- including about 100 that sell gas.
9. Safeway (average savings: 5.8 cents per gallon): This supermarket chain has more than 1,000 stores in the United States and Canada, many of which offer gasoline.
8. Smith's (average savings: 6.2 cents per gallon): Smith's operates some 130 grocery stores in seven Western states, with gas stations at around 80 locations. Kroger owns the chain.
7. USA Gasoline (average savings: 8.5 cents per gallon): This chain, a unit of Tesoro, runs some 100 gas stations in the Western United States.
6. BJ's Wholesale Club (average savings: 9.3 cents per gallon): Roughly half of the 200 stores that BJ's operates in 15 Eastern U.S. states sell gasoline. Annual club memberships start at $50.
5. Sam's Club (average savings: 10.1 cents per gallon): Sam's Club, a Wal-Mart subsidiary, offers gas at some 500 of its more than 630 U.S. sites. Basic memberships cost $45 a year. Some stations also let the public fuel up, but give members an extra 5 cents a gallon off.
4. Fred Meyer (average savings: 10.2 cents per gallon): Fred Meyer, another Kroger division, operates 132 supermarkets in Alaska, Idaho, Oregon and Washington. Some 90 of the sites sell gasoline.
3. Quik Stop (average savings: 12.5 cents per gallon): This Kroger-owned chain sells gas at roughly 100 convenience stores across Northern California and north Nevada. DeHaan suspects Quik Stop charges low pump price to get customers into stores for food, drinks and other items.
2. Arco (average savings: 13.5 cents per gallon): Arco operates 1,300 gas stations in the Western United States and says high sales volume allows it to charge low pump prices. Another Tesoro subsidiary, Arco also keeps prices down by not taking credit cards and charging customers 35 cents to pay with debit cards.
1. Costco (average savings: 14 cents per gallon): Costco has some 460 U.S. wholesale clubs in 41 states and Puerto Rico, and all but around 85 offer gasoline. Membership starts at $55 a year.