Is your car's gas-mileage gauge overstated?

With high gas prices, drivers are feeling pain at the pump. Drivers are becoming increasingly concerned with gas mileage when purchasing new cars. Be weary when asking about gas mileage though, GreenCarReports explains that gas-mileage gauges may be overstated. 

Gene J. Puska/AP Photo/File
A motorist pumps gas at a Mount Lebanon, Pa., mini-mart. GreenCarReports explains that gas-mile gauges may be overstated.

It's one of the most common questions asked of any new car: "So what kind of gas mileage does it get?"

The answer most often comes from the car's gas-mileage readout on the dashboard, generally specified to the tenths of a mile per gallon.

But as Edmunds determined, those readings vary considerably in accuracy. 

5 percent too high

A recent article in The Detroit News notes that the readouts are about 5 percent too optimistic in most vehicles.

But some are worse than others: Edmunds tested the old 2010 Ford Escape Hybrid and found its digital reading to be 19 percent overstated.

Similarly, a 2009 Volkswagen Jetta TDI diesel was 15 percent too high--possibly contributing to owners' experiences of diesel Jettas overachieving on their EPA fuel-efficiency ratings.

The only truly reliable way to ascertain a car's gas mileage is to test it over a sufficient number of miles that the tank can be all but drained several times.

Six or eight full tanks, at perhaps 300 or 350 miles apiece, means accumulating 1,800 to 2,800 miles on the car.

Ideally, it's filled at the same gas pump every time, at the same time of day--and each different car that's tested is run over a similar mix of city, suburban, and highway driving.

One weekend not enough

For many outlets that road-test new cars, including Green Car Reports, it's often not possible to keep the car that long or put that many miles on it.

Instead, we usually test a car over a long weekend, covering 300 or more miles in roughly the same mix: two-thirds highway (to get out of the city) and then one-third local duty, comprised of city and suburban errands, shopping, and so forth.

Over more than 100 cars, we've found that most vehicles fall roughly in line with their EPA combined ratings.

There are exceptions, though: The Mazda CX-5 and Mazda 3 with SkyActiv engines that we tested both handily exceeded their EPA ratings.

On the other side of the scale--as has by nowbeen widely documented--the Ford C-Max Hybrid didn't achieve real-world mileage anywhere near its 47-mpg EPA rating.

Last month, Ford lowered that rating to 43 mpg, and said it would pay existing 2013 C-Max Hybrid owners for the difference in gas costs. Most C-Max owners seem to come in at 36 to 42 mpg.

Best buy: less car than before

In the end, we'd suggest that the best way to maximize your gas mileage is to buy the smallest vehicle that meets most of your needs.

Think carefully about whether it may be cheaper overall to rent a larger vehicle for the one or two times a year you need it, rather than buying a car that will do absolutely anything you may need.

After that, drive gently and conservatively--and think about combining trips, doubling up with friends, neighbors, or coworkers; and otherwise trying to use your car only when necessary.

By all means, pay attention to the digital gas-mileage gauge. Just don't take it as the literal truth.

You've read  of  free articles. Subscribe to continue.
Real news can be honest, hopeful, credible, constructive.
What is the Monitor difference? Tackling the tough headlines – with humanity. Listening to sources – with respect. Seeing the story that others are missing by reporting what so often gets overlooked: the values that connect us. That’s Monitor reporting – news that changes how you see the world.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to

QR Code to Is your car's gas-mileage gauge overstated?
Read this article in
QR Code to Subscription page
Start your subscription today