Taking A Detailed Look At Why 'Your Mileage May Vary'

It's safe to say that mileage claims are controversial at best, and often inaccurate.

"There are three types of lies: lies, damned lies and statistics," goes the old quote variously attributed to Mark Twain, Benjamin Disraeli and other wits. Were they writing today, they'd probably add a fourth: fuel economy numbers.

As regular readers have heard, Hyundai is being sued for allegedly misleading mileage ads. Honda, meanwhile, beat back one Civic Hybrid owners mileage lawsuit upon appeal but also agreed to a settlement covering thousands of others who didn't get nearly what the automaker promised.

Without taking sides in these individual cases. it's nonetheless safe to say that mileage claims are controversial at best, and often inaccurate, at least in terms of what real world driving is likely to yield.

"Your mileage may vary" is a disclaimer we've all heard, and certainly there are enough variables that impact what your car, truck or crossover will deliver: such factors as the speed you drive, what altitude the vehicle is operated at, what fuel you use, whether your tires are properly inflated and how many passengers you've got crammed into the backseat. And considering the added bulk too many of us carry around our middles, even that can play a role.

Paul EisensteinPaul A. Eisenstein is Publisher of TheDetroitBureau.com and a 30-year veteran of the automotive beat. His editorials bring his unique perspective and deep understanding of the auto world to Autoblog readers on a regular basis.

The challenge has been to come up with valid test procedures that come anywhere close to replicating real-world conditions.

But there's no question that manufacturers clearly want to put the best face possible on their products and, like that speed-talking spokesman for FedEx some years back, fuel economy disclaimers may be overlooked entirely.

The so-called Monroney sticker, the window label found on all new automobiles sold in the States, dates back to 1958 and legislation sponsored by Oklahoma Senator Almer Stillwell Monroney. Fuel economy numbers were added in the 1970s when Congress authorized the Environmental Protection Agency to oversee the new Corporate Average Fuel Economy [CAFE] standard and to begin testing every new vehicle entering the market.

The challenge – then and now – has been to come up with valid test procedures that come anywhere close to replicating real-world conditions. To help individual motorists adapt the numbers to their own driving styles, the EPA went to a three column approach, with city, highway and combined ratings.

The EPA employs only about 20 staffers to run mileage tests and they process barely 15 percent of all the new products that come to market each year.

In reality, the EPA employs only about 20 staffers – less than 0.1-percent of its staff – at its Ann Arbor, Michigan outpost to run those tests and they process barely 15-percent of all the new vehicles that come to market each year. For the rest, they take the manufacturers at their word, though random testing – much like the more extensive screening travelers occasionally experience at the airport – is intended to keep everyone honest.

For the 200+ vehicles that are subject to actually testing, the federal agency uses a dynamometer, the automotive equivalent of a treadmill. The computer-controlled devices can simulate such factors as road friction and wind resistance – but specially trained staff actually do the "driving," carefully obeying instructions displayed on a computer monitor to ensure uniform speed, acceleration and braking behavior that can be readily duplicated from one vehicle to the next.

The raw data goes through an incredible amount of finessing to account for such things as the use of air conditioning and other accessories. And the EPA has routinely tweaked the results to reflect increased highway speeds and changes in driving patterns.

Given the choice, it's no surprise that automakers flaunt the high-mpg highway results.

It's also had to adapt to technological changes, such as the increased use of all-wheel drive and, most recently, the emergence of battery-based powertrains. The numbers you see on the Monroney today reflect big changes that went into effect for the 2008 model year – driven by the fact that early-generation hybrids routinely performed significantly better in EPA testing than on the road – despite what those hyper-milers might tell you.

Those changes over the years add up. Without these corrections, the unadjusted mileage for the typical vehicle sold in the U.S. in June would have been an even 29.0 mpg. The average Monroney sticker was just 23.6, however – though both figures represent a 17-percent increase from when the University of Michigan Transportation Research Institute, or UMTRI, began tracking the data in October 2007.

Anyway, that's how we wind up with the numbers you see. Or should see. But given a choice of promoting a 28 mile per gallon city-cycle figure, a 32 mpg combined number or the highway-rated 40, well, it's probably no surprise that most (read: "all") car companies flaunt the open-road results. (The exception being hybrids, which typically do better in stop-and-go driving that recharges their batteries.)

"We'd like to advertise the figures closest to what an owner should get... but if we did that we'd be at a competitive disadvantage."

And that's where the debate that could land Hyundai in hot water comes in. And it's not alone.

"We'd like to advertise the combined numbers because those are the figures closest to what an owner should get day-to-day," said an official with a major Japanese competitor who asked not to be identified by name, "but if we did that we'd be at a competitive disadvantage."

That's also why makers will continue to use whatever the EPA reports even if they know the figure is inflated. In May, California Superior Court Judge Dudley Gray II overturned a small claims court judgment that originally went in favor of Civic Hybrid owner Heather Peters. "Federal regulations control the fuel economy ratings posted on vehicles and advertising claims related to those fuel economy ratings," he wrote in his verdict.

An automaker is legally entitled to lower the figures if it believes they are inaccurate. Fat chance.

In fact, that is not the correct interpretation of the law, according to the EPA itself. The figures the agency quotes are the maximum a maker can use but it is legally entitled to lower the figures if it believes they are inaccurate.

Fat chance. Unless someone blinks, or the courts or regulators step in, it's likely you'll continue to see automakers focus on the biggest numbers they can get away with using – putting the rest in the smallest print they also can get away with.

Paul EisensteinPaul A. Eisenstein is Publisher of TheDetroitBureau.com and a 30-year veteran of the automotive beat. His editorials bring his unique perspective and deep understanding of the auto world to Autoblog readers on a regular basis.

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    • 1 Second Ago
      • 3 Years Ago
      For some reason Hyundai/Kia vehicles are extremely sensitive to driving style much more than any other car. My DD is a 2005 Aviator rated at 13city 18highway (adjusted to 11/16 under the new EPA test). When I first bought it and was driving it around town like I stole it the lowest MPG I ever got was 13.2mpg. I still like to punch the gas pretty frequently but my new commute is about 50% city and 50% suburban (long-ish roads with stop lights every mile or so) and I get 16-16.5mpg with no problem, even on winter blend fuel. Motortrend's long-term Elantra which had 16,000 miles and a decent amount of highway driving in the mix returned 26.9 MPG overall. Less than the city-only estimate. In the most recent compact crossover comparison by Motortrend, the new Ford Escape with the EcoBoost engine returned 21.4 MPG overall and the Kia Sportage returned the worst mileage of only 15.8 MPG. All 5 cars were in the test were driven on the same roads, through the same performance tests, by the same drivers. In theory, if the cars were being driven hard for performance testing the turbocharged engine in the Escape should have taken a major hit in fuel economy, however the Kia returned mileage almost 5 MPG worse than the runner up Tiguan.
      • 3 Years Ago
      For 2013 the Monroney label will have the combined fuel economy displayed as the largest number. Now, if teh FTC or FCC or whatever organization would make automakers display the combined figure in their advertising...we'd be a lot better off. That said, I've had no issue drastically exceeding EPA estimates in ANY car that I drive.
      • 3 Years Ago
      on the EPA web site that gives estimated mileage of all vehicles there is a place on each where owners can list what the get. They are then averages for all owners and given by range. Checkit out, very interesting. www.fueleconomy.gov.
      • 3 Years Ago
      one manufacturer seems to have a pile of mounting evidence against it. hyundai and kias all seem to fall way below their sticker claims http://tinyurl.com/7zpbd4j
      • 3 Years Ago
      Please don't believe the "AVG MPG" meter in your car, either. Unless you're taking total miles driven, divided by gallons put in the car, then I don't believe what your MPG is. I calculate my MPG via Fuelly.com after each fuel up, and it's always a 1 1/2 MPG lower than what the car calculates. Fuelly.com is a GREAT site if you want to see what some people are averaging in their cars "real world". Certainly more reliable than EPA stickers.
      • 3 Years Ago
      I've actually been in the UMTRI building working on a project, and almost took an internship there. I had no idea they did the EPA fuel tests there. Small world.
      • 3 Years Ago
      I have a 2012 Sonata SE with the 2.4L and the MPG on the Monroney is 24city/35hwy with average of 28. I average right at 30MPG. I get 37 regularly on the highway and 25 in town and I do not let many people beat me off the line at a stop light. It does what it is supposed to and looks great doing it!
      • 3 Years Ago
      My last two cars (2003 SVT Cobra and 2011 Lexus IS) have been understated all around. I tended to see about 10-15% higher MPG on the Ford and about 5-10% higher on average for the Lexus. I also had a Lexus CT200h loaner that was pulling in pretty drastically higher MPG on the highway than the the EPA rated it. I've rented a Prius plenty of times and it's pretty spot on.
      • 3 Years Ago
      Fuelly is not perfect, but it is a great stepping stone to find out real world mpg of a car you are looking at getting
      • 1 Month Ago

      Surely it cannot be that hard to test the cars under real life driving conditions in order to give a more accurate result? Aren't the mpg official results monitored by a body, or are Hyundai and Kia fiddling the results?

      It is claimed that you need to knock off 30% of the manufacturer's claims to be close to the actual mpg of the car. And after reading this article http://automotive-hub.blogspot.com (tests in Europe) it does not surprise me at all....I wonder how this testing compares to USA?

      • 3 Years Ago
      Women drivers..........God help us !
      • 3 Years Ago
      Its the drivers fault, My sister is one example, she bought a new honda fit and only gets 27mpg, but she has the A/C on all the time, drives like a maniac, always doing about 80 on the freeway, but that is how traffic moves in this area, then she complains the car is not getting over 33 mpg like its supposed to. People need to understand that the sticker does not say (always will get 40mpg) , it says (up to 40mpg)
        • 3 Years Ago
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