How Far Should You Drive to Save a Few Pennies?

By Timothy C. Barmann, The Providence Journal, R.I.

May 16–How far would you drive to buy cheaper gasoline?

With the average price of gasoline now more than $3 a gallon, it might seem prudent to search for the least-expensive station.

“Every little bit helps, you know,” said Allison Ahrens, of Cranston, as she filled up her Ford Focus at a station in Seekonk yesterday.

But if you drive a few miles out of your way to save a few cents at a cheaper station, it may not save you any money at all.

That’s because you have to consider the cost of the extra gasoline you’ll burn in your quest for a bargain.

Take Eliana Arteaga, a caretaker who works in Rehoboth. Yesterday, she drove from Rehoboth to Seekonk to fill up her Toyota Echo at an Exxon station. She said she made the drive because she knew some gas stations in Seekonk were usually less expensive than those in Rehoboth. In fact, that was true yesterday — she found that gasoline in Seekonk was $2.979 a gallon, 4 cents cheaper.

But it appears that Arteaga’s efforts to find the best price may have actually cost her more money. With the help of fuel economy ratings from the Department of Energy, a driving-distance estimate from Google Maps, and an online gasoline calculator devised by The Journal, we ran the numbers.

Arteaga drove about 10 miles, round-trip, to buy 8.9 gallons of gasoline in Seekonk. The whole purchase cost about 36 cents less than it would have in Rehoboth.

Her car gets about 35 miles per gallon in the city, which means she used a little more than a quarter-gallon of gasoline just to get to the cheaper station. At $3 a gallon, that extra fuel cost her about 86 cents.

The bottom line: Arteaga spent an extra 86 cents in order to save 36 cents. She would have saved 50 cents if she had bought the more expensive gasoline in Rehoboth. And she certainly would have saved time, plus wear and tear on her car.

Try the Journal’s online calculator yourself to find out when it makes sense to drive around for the best price: http://www.projo.com/gaschart

The calculator asks you to enter four factors: how much gas you’ll buy, the average price of gasoline, the miles-per-gallon rating of your car, and how far out of your way you will you drive to the less-expensive station.

(The Department of Energy has a tool to look up a car’s MPG rating at http://www.fueleconomy.gov/feg/findacar.htm)

As you might expect, the more fuel-efficient your car, the farther you can drive and still save money. Likewise, the more gasoline you buy, the more it makes sense to shop around.

However, the more expensive gasoline becomes, the harder it is to justify extra driving for cheaper gas.

Here’s an example. Assume a car gets 20 miles per gallon and takes 15 gallons of gasoline during a fill-up. When the average price of gasoline was $1.50 a gallon, it made sense to drive an extra five miles to save five cents a gallon. The net savings: 38 cents.

But with gasoline at $3 a gallon, it costs more to get to the cheaper station and the extra driving wipes out the savings. The cost of the extra fuel used is equal to the amount saved by buying the cheaper gas.

(Yesterday’s average price was $3.009 a gallon, according to a survey by the State Energy Office. That’s up 7 cents from last week.)

Of course, it’s always prudent to buy gasoline at a cheaper station along your usual route. AAA Southern New England’s gas survey yesterday found a wide range of prices in Rhode Island for regular, self-serve gasoline: $2.879 to $3.099.

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