Gap Between Advertised And Real World Fuel Economy Doubles In A Decade


On some level, we all know that automakers advertised fuel economy numbers are a bit…optimistic, shall we say. So while there may be a glut of 40 mpg compact cars on the market right now, there has been some hearsay that the real world numbers rarely align with the advertised numbers, no matter how catchy the slogan used to sell them.

Now a new study done on European cars shows that the gap between advertised fuel economy and real world numbers has more than doubled, from 8% in 2001 to 21% in 2012. The study collected information from 28,000 user-entered entries in a German fuel economy database Europe has been implementing greenhouse gas reduction targets for decades, though they have become increasingly onerous in the last ten years.

The study uses CO2 emissions to factor average fuel economy, and what they found is that in the real world, vehicles were about 21% less-efficient than advertised. As I said, I think we all, on some level, realize that the advertised numbers are a bit generous. Over in Europe though, the study slams automakers and government officials alike. The paper says there is a high tolerance for exploiting loopholes and running fuel economy tests under impossibly optimistic conditions (flat roads, cold-start testing, no air conditioning on). The study also says the NEDC road testing standards are insufficient and do not represent real world driving conditions.

Automakers naturally want to tout high fuel economy at a time of high gas prices. However, it seems there is a lot of voodoo at work when it comes to achieving these impressive numbers…and it isn’t just a problem in Europe. Hyundai has been sued by consumer groups for misleading customers on fuel economy in the U.S., and Honda has just settled a lawsuit with Civic Hybrid owners who saw half the advertised fuel economy in the real world.

In other words, take any advertised fuel economy with a healthy spoonful of salt. You, the driver, are the most important factor in determining your overall gas mileage. On the same token, it’s kind of crappy how the government knowingly lets automakers lie to the car-buying public. Just another example of corporate cronyism run amuck.

Source: Green Car Congress | Image:Fuel Gauge via Shutterstock

About the Author

A writer and gearhead who loves all things automotive, from hybrids to HEMIs, can be found wrenching or writing- or else, he's running, because he's one of those crazy people who gets enjoyment from running insane distances.
  • Josh G

    My Car is rated for 33MPG highway 22something city, not sure exactly of the city #.
    My Daily commute is 38 miles each way, mixture of highway driving, stop and go traffic, and mild city driving. I Average 33MPG in the winter, and 35-36 in the summer.
    If i drive like an old mane i can get 38MPG, but i don’t like to be cut off that much.

  • Roy I

    I’ve owned 12 cars since 1976 and I have beat the EPA mileage estimates with all of them by 10% to 20%. It’s even easier now since the EPA made their estimates more conservative. Anyone can do it if they learn how to drive for maximum gas mileage.

    • @ Roy I

      Sure, anyone can achieve great fuel economy by driving 55 mph in the right-hand lane all day every day. But in a world where even the cheapest cars come with close to 150 horsepower, people simply drive faster.

      Furthermore, I think the EPA standards are woefully out of date and not at all contingent on real-world situations that most of us often find ourselves in.

  • They advertise the EPA ratings — you make it sound like they make ’em up.
    A rating is not a guaranty. Year round I average 40-75% *over* the EPA rating. Anybody can be a leadfoot, but it takes practice to learn to ecodrive.


  • I think, Chris, this has as much to do with distracted driving as anything else. If people pay attention to the road and keep their eyes up, they can coast to stops, apply smoother inputs, and maintain momentum rather than stop suddenly, ride their brakes while texting/talking, etc.

    I’ve been stuck behind people on roads slowing down and speeding up by as much as 10-15 mph in between texts or while talking with their hands. All of that is bad for mpg.

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  • Tim

    I have a 2011 VW TDI Jetta. It is rated at 42mph highway. I drive about 50 miles each way to and from work each day. I don’t drive conservatively. I drive 70 to 75 mph about 70% of the way in to work and have a few short cuts to avoid heavy traffic that is faster but adds stop lights and signs. I get 46 to 48 MPG. A bit better in the summer due to changes in the formulation of diesel fuel in cold weather. In past years, I almost never got close to the EPA estimate. Based on my experience, I’d say the estimates are getting better not worse. My wife’s car is a Prius – same situation. She always gets better than the rating.

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