By on May 17, 2016

2016 Chevrolet Traverse

The strange case of General Motors’ incorrect fuel economy numbers is getting stranger, if it wasn’t odd enough already.

GM announced late last week that it would reprint EPA labels for its 2016 full-size crossovers after the wrong mileage made its way onto window stickers, but Consumer Reports now says there’s something fishy about that.

The official word was that undisclosed changes made to the 2016 GMC Acadia, Chevrolet Traverse and Buick Enclave required the printing of new mileage figures, which, due to a faulty “data transmission,” overstated mileage by one to two miles per gallon.

The vehicles’ powertrain hadn’t changed between this year and last, leaving many to wonder what changes could have been made that would actually lower fuel economy on a newer vehicle.

As Consumer Reports points out, the revised mileage for the 2016 models is lower than that of previous model years. In the case of an all-wheel-drive Acadia, a corrected EPA label for the 2016 model shows a 2 mpg (combined) drop from 2015.

It also means the older range of vehicles beats new models for fuel economy going all the way back to 2007.

Oddly (or ominously, however you want to look at it), when the publication compared the EPA figures for past models with its own observed fuel economy results, the combined mileage from their tests was 2 to 3 mpg lower than the EPA’s. That places the real-world mileage of the older GM triplets closer to the revised 2016 mileage than what was printed on their window sticker.

When contacted, a GM spokesperson told them that “no other models or model years were affected” by the mileage discrepancies.

The EPA asked GM for all data related to the 2016 mileage discrepancy, but it’s unknown if they requested any data dating to previous model years. Either way, the EPA didn’t respond before the report was published.

About two million of the General’s full-size crossovers left dealer lots since they went on the market. If past fuel economy numbers turn out to be inaccurate, it could mean a hefty amount of gasoline expense compensation for GM, a la the Hyundai/Kia controversy of four years ago.

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41 Comments on “GM’s Flawed Fuel Economy Numbers Could Affect Millions of Vehicles...”


  • avatar
    VoGo

    Lawyers at Ren Cen are hard at work tonight, fabricating evidence that the MPG labels were printed by “old GM” pre-bankruptcy, and are not the responsibility of “new GM”.

    • 0 avatar
      qfrog

      Maybe they take some inspiration from their Opel division’s handling of the diesel situation.

      I’m sure you’ll find that when the vehicle is below certain elevations, or operating above/below certain temperatures and when the engine is rotating above a certain RPM… the fuel injection duty cycle is increased as a means of protecting the engine against damage or accident and for safe operation of the vehicle.

    • 0 avatar
      RobertRyan

      GM could say they are not Mitsubishi and are doing something about it LOL

  • avatar
    SCE to AUX

    Magazine testing of MPG figures is nearly meaningless. Only testing per the EPA protocol is relevant.

    • 0 avatar
      psarhjinian

      Not in CR’s case.

      Their instrumented testing a very good complement to the EPA cycle figures (it’s measured via splicing of the line, not via fillup) and it’s certainly relevant in an era when OEMs are tuning ECUs to the EPA test.

      • 0 avatar
        30-mile fetch

        +1. It is as close to a standardized methodology under real world conditions as you will get. This isn’t Car and Driver hand calculating fuel economy at the pump after hooning and testing it in who-knows-what manner.

        • 0 avatar
          Frylock350

          Car and Driver is a great fuel economy reference in a way; it sets a floor. I can look at their numbers and know I’ll never get that bad of mpg. Or in the case of me buying a Camaro or something it gives me some more real world numbers.

  • avatar
    NormSV650

    We got 26 mpg in a rental 2015 Enclave Leather FWD all highway at the speed limit. Two way average for an hour each way according to the trip computer.

    • 0 avatar
      CoreyDL

      Speed limits vary by state.

      • 0 avatar
        APaGttH

        Terrain too. If I’m going over the Snoqualmie Pass and then southeast to Yakima over all those ridges, my G8 is never seeing 24, the Avalanche is never seeing 21, the Saturn van (retired) would never see 23, and the wife’s Subbie never sees 28.

        When I lived in South Dakota and Texas, I typically exceeded highway MPG. Long, flat, straight, and not a lot of traffic causing speed up and slow down. Could set the cruise and drive. Optimized MPG.

    • 0 avatar
      VoGo

      Before or after Trifecta Tuning? Inside Area 51 or above it? With or without Amelia Earhart driving?

    • 0 avatar
      gtemnykh

      Norm in the 26mpg Enclave and DeadWeight in the mythical “31mpg @75mph” Durango should compete head to head in a fuel economy test. In this case, Norm’s claims are actually more believable.

      • 0 avatar
        Frylock350

        I can buy a 26mpg Enclave. I’ve gotten 24.5 mpg on flat straight highway with my Silverado with the cruise set at 64mph. The smaller more aerodynamic Buick with a lower output engine should be capable of better in ideal conditions. Then again I find that with the right conditions you can beat the EPA on just about any vehicle. 31mpg in a Durango? I’ll believe that when I see it. My experience with them is that a Tahoe gets better mpg.

  • avatar

    Individual testing of mileage is irrelevant. Everyone’s driving style, mass carried, time-in-traffic…it’s all different.

    • 0 avatar
      Frylock350

      @BTSR,

      You can add use of the remote starter to that list too. I know people who let their car run for 15 minutes before driving it. That’s alot of rich burn fuel in the winter. Then other factors like temperature; humidity, altitude, etc also factor in.

  • avatar
    tomLU86

    The trip computers aren’t always accurate, and when they are off, they tend to be optimistically.

    Ironically, my 2011 Malibu is the most accurate trip computer I’ve had, and pretty close.

    If you really want to know, you need to log the miles and top off the tank, repeat several times in a row, and take the overall (this will compensate for filling variation). The bigger the fill-up, the more accurate the reading.

  • avatar
    Upthewazzu

    Not surprised. I had a ’13 Malibu 2LT w/2.5L 4-pot and never got advertised mpg. I have a light foot, and couldn’t get there. Many many complaints online, and I think CR even stated the mileage was never as good as advertised.

  • avatar
    APaGttH

    Isn’t going back to 2007 disingenuous, beyond creating clickbait, because MPG calculations changed in the 2008 model year. MPG stickers are BS anyway, but they were completely, “ya, good luck with seeing that mileage, it is never going to happen,” BS through 2007. IIRC.

    • 0 avatar
      Richard Chen

      Lambda fuel economy ratings were unchanged from MY2007 vs. MY2008. The FWD improved 1 mpg city for MY 2009, presumably thanks to direct injection, and stayed the same through 2015.

      As if the class action attorneys have nothing better to do…

    • 0 avatar
      Frylock350

      @APaGttH,

      I always viewed MPG stickers as a way to compare cars; not get a good estimate of real world economy. They may not tell me what real world mpg I can expect from vehicle X; but they can tell me that vehicle X is better/worse than vehicle Y.

  • avatar
    Big Al from Oz

    Who is the worst and most deceitful auto manufacturer??

    General Motor or VAG?

    I’d bet this site will lean on GM’s side for the most decent??

    GM should pay the price like VAG.

  • avatar
    Blackcloud_9

    I like GM cars. And I really want to like GM. I think they often get the short end of the stick in sites like this. But when stuff like this keeps happening… Man…They are running out of feet to shoot themselves in.

    • 0 avatar
      ponchoman49

      Yeah it’s not like Toyota, Hyundai or Mitsubishi ever once lied or overstated there mileage and power ratings on there engines right? Or how about Ford in the 90’s with there 5.0 V8 having to downgrade HP from 225 to 205 because they were using the high end of the average instead of a real median average for the rating. And lets not forget the recent Ford C-Max and Fusion hybrids with overstated MPG. That never happened either right?

  • avatar
    zip89105

    The bottom line is: NO ONE CARES. If I purchased one of those vehicles it sure wouldn’t be because of the mpg.

    • 0 avatar
      rpn453

      Speak for yourself. A lot of people consider fuel economy ratings to be an important factor when purchasing a vehicle; possibly even most. Those people may have been defrauded.

      I don’t agree with the testing methodology of the EPA ratings, but even I take them into consideration. There is some value to them.

      • 0 avatar
        NormSV650

        Our 2015 Terrain 2.4l has seen 30+ and rising on the highway at the speed limit…with AWD.

        My Mom’s LaCrosse with 2.4l was seeing 26 mpg in all city driving with me behind the wheel. It’ll beat Avalon Hybrid on the highway at 30+ that Car & Driver got. That car with the lighter 4-cylinder up front is very tossable and fun to drive in the tighter turns for a big car.

  • avatar
    rpn453

    GM does have a history of questionable fuel economy ratings for their CUVs.

    https://www.thetruthaboutcars.com/2010/02/why-the-chevy-equinox-epa-mileage-numbers-dont-add-up/

  • avatar
    makuribu

    The EPA tests produce ideal laboratory (ie fantasy) numbers comparable only to other EPA fantasy numbers, not to real world conditions of any sort. Remember, this is the origin of the phrase Your Mileage May Vary. And since it all depends on self testing/reporting, there is another level of delusion/deceit possible.
    The right way to do it, and the most fun way, is a massive track day. CR and various university automotive engineering departments bring calibrated instruments and ASTM methods. Volunteer drivers (me! me! me! pick me!) drive every model around some NASCAR oval for several dozen laps on cruise control with everything instrumented out the wazoo. And make the Mexicans, er, I mean manufacturers pay for it.

  • avatar
    ponchoman49

    Funny but I don’t remember all this fuss being made from CR when the 2008 Prius dropped from a claimed 61 MPG city down to a more realistic 48 from previous years when manufacturers had to adjust ratings for stricter more realistic conditions. Most vehicles lost between 1-3 MPG in the changeover but the Prius dropped by a massive 13 for the city rating and 7 on the highway.
    Now it’s a huge deal that a sticker was mis-printed that was off by 1-2 MPG. 22 highway MPG on the Lambda’s was always the rating all along on the Buick Enclave with AWD. 23 was the rating on the Traverse and Acadia also with AWD due to less weight and typically smaller tire sizes. It sounds to me like GM is trying to cover there rear ends by just rating all 3 at the new 15/22 figure in AWD trim which makes sense considering that the latest models have more and more equipment being ordered on them and larger 19 and 20″ tire sizes are more frequently being ordered which is proven to reduce MPG some.

    • 0 avatar
      Drzhivago138

      That last third of the paragraph was one sentence.

    • 0 avatar
      VoGo

      2008 was a change in methodology; at no point was Toyota accused of lying about the mileage of the Prius.

      • 0 avatar
        ponchoman49

        Then why are there loads of consumer complaints claiming they got nowhere near that 61 figure?
        Why did every other car company drop by 1-3 MPG on there vehicles and the Prius went down by a huge 13 MPG.
        Of course nobody is going to admit that Toyota was far overstating the Prius’s mileage by such a large figure. In the real world it was way off for many consumer’s including several co-workers that bought into these cars after gas went up to 4.50 a gallon. They were typically seeing 36-43 in everyday driving and few ever claimed 61 unless they were chronic hyper milers.

        They should have been accused of overstating the mileage is the point I was trying to make. If it was a GM product that was re-rated by 13 MPG less on the new “methodology” as you state there would have been multiple investigations on why that was by CR and probably every rag imaginable at the time.

        • 0 avatar
          Quentin

          Ponchoman – the amount changed does not matter because mpg isn’t on a linear scale. If you look at it from a pure cost perspective, the 2mpg difference on the GM SUVs means that you will burn 37 gallons more of fuel than expected over 10k miles (24mpg versus 22mpg). The Prius would burn 26 gallons more of fuel over 10k miles (51mpg versus 45mpg). So, even though the absolute mpg number was off by more on the Prius, the 2mpg difference in the GM is actually more costly for the customer.

    • 0 avatar
      KixStart

      There was no point singling out the Prius, since the test was optimistic for all cars… if unusually friendly to the Prius.

      I’ve owned several Toyotas, including a Prius. On trips, every one of my Toyotas routinely beats its highway number. Other makes I’ve rented do not do so well. If there’s a pattern of deceit at Toyota, I don’t see any evidence of it.

  • avatar
    Lack Thereof

    “The vehicles’ powertrain hadn’t changed between this year and last, leaving many to wonder what changes could have been made that would actually lower fuel economy on a newer vehicle.”

    Well, I dunno, the obvious answer would seem to be reprogrammed shift points, holding gears a few hundred RPM longer and downshifting quicker. With the competition all outclassing them in HP, they have to do something to compete.

    That seems like something easy to check & verify, because I really don’t see any other possibility.

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