EPA MPG values reported for 2016 Prius very misleading

Discussion in 'Gen 4 Prius Fuel Economy' started by Gokhan, Mar 8, 2016.

  1. Gokhan

    Gokhan Senior Member

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    MODIFIED POST

    EPA did a really poor job of reporting the MPG values for the 2016 Prius. There are many trim levels and they aren't clearly specified in their numbers other than "Prius" vs. "Prius Eco".

    After studying the EPA data, these might be more appropriate values:

    MPG (city/highway/combined)

    Prius Two (NiMH battery): 57/52/55
    Prius Two Eco: 58/53/56
    Prius Three/Four: 56/51/54
    Prius Three/Four Touring (larger wheels): 55/50/53


    So, Prius Two has the worst fuel economy thanks to its inferior NiMH battery. Prius Two Eco is only slightly better than Prius Three/Four thanks to its slightly lighter weight. Prius Three/Four Touring has slightly worse fuel economy than Prius Three/Four thanks to the larger rotational inertia (moment of inertia) of larger wheels.

    Below is the data from Test Car List Data Files | Cars and Light Trucks | US EPA and reasoning:

    Prius 16-ZV3H/2 (possibly Prius Three/FourTwo, slight MPG penalty thanks to added weight)

    HWFE 76.1 MPG
    Cold CO 55.4 MPG
    Federal fuel 2-day exhaust (w/can load) 77.3 MPG
    US06 48.6 MPG
    SC03 52.3 MPG

    Prius Two Eco 16-ZV2H/0 (not much artificial/calculated MPG gain from slightly heavier Prius Two)

    HWFE 76.9 MPG
    Cold CO 56.6 MPG
    Federal fuel 2-day exhaust (w/can load) 84.1 MPG
    US06 50.1 MPG
    US06 51 MPG
    SC03 58 MPG

    Prius 16-ZV3H /1 (possibly Prius TwoTwo with heavy loading)

    HWFE 63.6 MPG
    Cold CO 50.8 MPG
    Federal fuel 2-day exhaust (w/can load) 64.9 MPG
    US06 42.9 MPG
    SC03 46.9 MPG
    SC03 45.4 MPG

    Prius 16-ZV1H 2/3 (possibly Prius Three/Four, some MPG penalty thanks to added weight)

    HWFE 71.2 MPG
    Federal fuel 2-day exhaust (w/can load) 78 MPG
    US06 48.6 MPG
    Cold CO 56.3 MPG
    SC03 58.8 MPG
    SC03 58.1 MPG

    Prius 16-ZV1H /1/16-ZV2H /5 (Prius Three/Four Touring, more MPG penalty thanks to larger wheels)

    HWFE 66 MPG
    Federal fuel 2-day exhaust (w/can load) 71.1 MPG
    US06 45.5 MPG
    Cold CO 51.7 MPG
    SC03 51.9 MPG
    SC03 51.3 MPG
     
    #1 Gokhan, Mar 8, 2016
    Last edited: Mar 9, 2016
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  2. Trollbait

    Trollbait It's a D&D thing

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    How do you figure the touring models do better than the base, when the OP of the other thread concluded they did worse?

    Not the EPA's fault though. The rule allowing a car to use the rating of another car with the same drive train and similar weight is still in effect, and it might take an act of Congress to change it. It is the manufacturer's choice to use and/or abuse it.

    I know there are two EPA engine codes for the Prius; one for the lithium battery and one for the nickle one. That code reflects the drivetrain and emission system, and the rule might apply to the drive train(engine and transmission) only. Since the hybrid battery is considered part of the emission system, Toyota could still use the above rule.
     
  3. bisco

    bisco cookie crumbler

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    o/p, you're a smart guy, you know the epa does a poor job with all testing. it's not misleading, but for comparison purposes only.
     
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  4. alanclarkeau

    alanclarkeau Senior Member

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    I don't think that you could ever get a perfect figure. It just takes a heavier driver, (or one with a heavier right foot) to make a bigger difference than wider wheels or a spare tyre.

    In Australia, there's a push to have MPG (actually l/100) figures made more "realistic".

    But in reality, it's a measure of what the car actually did on a set, and comparatively equal test. Yes, it's possible that manufacturers manipulate it somewhat.

    The problem is, that most people report using 10%+, or maybe even 50%+ what the standardised test gave. And then demand that the test be changed. But, my observations are, that it's the way most people drive.

    Motoring journalists take the car for a test which includes several people, camera gear in the boot, acceleration and top speed readings on a track, city driving - and generally trying to find out how much fun it is to drive the car - and rarely get anywhere near the standardised test. But generally it's comparative between cars.

    I know that if "hypermiling" my Ford Fiesta Diesel, I can equal the test results. Similarly with some (not all) previous cars. Do I always drive like that. No!

    Being realistic, I look at the test results, and use them as a comparison.
     
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  5. mmmodem

    mmmodem Senior Taste Tester

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    So Toyota took a dive for mpg in selling a two with NiMH battery? Could they have just eliminated it and sold the ECO as their base model and advertise 58 mpg for all 2016 Prius? This EPA thing is so confusing. :confused:
     
  6. Gokhan

    Gokhan Senior Member

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    I think you are probably right that 2016 could be the last year the NiMH battery is offered.
     
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  7. krousdb

    krousdb NX-74205

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    When I looked at the Prius 16-ZV3H /1 data, I considered it an outlier. If you look at the Target Coefficient A, it is at 31, compared to 17 for the Eco, 18 for the non touring and 21 for the touring. That is a huge difference. No wonder that the MPG suffered. Since Coefficient A is not dependent on speed, it has to be more related to weight. I was thinking that this config was at fully loaded weight and that the Two Base model unloaded was Prius 16-ZV3H /2.
     
  8. stephane

    stephane Prius v owner

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    Toyota only offert NIMH in Canada on all model no other option....
     
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  9. AshleyTPriusv

    AshleyTPriusv Junior Member

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    For the base model upgrade package with the NIMH offered in Canada when I did my test drive I got 5.2l/100km (45.2336 mpg) and that was with me pushing the car to see how fast it would go up a hill, in a straight section of road and on the highway.

    I know it's rated for 4.5l/100km (52mpg) combined and I believe I can get those rating. So I really don't see how someone can get these US06 42.9 MPG, SC03 46.9 MPG, SC03 45.4 MPG rating all the time unless they have a heavy foot Or ssomething..

    My thought is that if your getting a bad fuel rating with your Prius maybe it's not the car but your driving techniques and where your driving (like up hills) and possibly how much laod your carrying.
     
  10. David Beale

    David Beale Senior Member

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    Actually the LiIon battery is used in Canada on the Technology package and the Touring package. But not on the "Prius" package. The standard package is the one found all across Canada for now. The other two packages are available only in Vancouver, Toronto, and Montreal.
     
  11. Trollbait

    Trollbait It's a D&D thing

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    The EPA doesn't actually run the test. It is done by the car company. The EPA will run audit tests on a selection of cars, but this is about only 10% of the car models sold in a given year. They might look into things if there is enough complaints about a particular car, but except for the most obvious errors, they most likely are only able to just sign off on the other 90% due to lack of manpower.

    Do you happen to know what test cycles Australia uses?

    No, the Eco's weight puts it into a lower weight class, so it and the other models have to be rated separate. Toyota can use the better non-Touring results for the Touring window sticker because they are all in the same weight class though.

    There is no concerns about charging NiMH when the pack has reached freezing temperatures, and its performance keeps up to colder sub-freezing ones than typical Li-ion chemistries.
    The larger wheels can really pull the fuel economy down. People swapping out smaller for larger on previus generations have reported seeing such drops.
     
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  12. wjtracy

    wjtracy Senior Member

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    The title of this thread should be "Gokhan's 2nd Hypothesis about Gen4 MPG". Toyota nor anyone else has never said the Li batt gives better MPG.

    A proven Hypothesis becomes a theory, but we have none yet.
     
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  13. bisco

    bisco cookie crumbler

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    you can't blame a guy for trying.:cool:
     
  14. Gokhan

    Gokhan Senior Member

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    Yes, the model I thought to be a Prius Three/Four appears to be a Prius Two according to the test-group code. I also noticed the higher load later.

    Well, here is Hypothesis 3: Test artifact/formula artifact? Should we really take the EPA stickers seriously?
     
  15. bisco

    bisco cookie crumbler

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    well, i bought a 2004, and the sticker said 60 mpg. then, i bought a 2008, and the sticker said 50 mpg. how seriously would you take them?
     
  16. wjtracy

    wjtracy Senior Member

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    I like hypotheses...I think they are all valid possibilities
     
  17. alanclarkeau

    alanclarkeau Senior Member

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    Sorry, I have no idea.

    Our Prius are all NiMH. Personally, I'm happy with NiMH - it's a tried and proven formula, and from what I read, most batteries are lasting the life of the car. The Li-ion, while probably having good life too, hasn't had the same time for the same longevity to be proven. I would envisage TOYOTA to have thoroughly tested them before putting them in service, but actual time sometimes tells another story.
     
  18. Gokhan

    Gokhan Senior Member

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    Any scientific experimental/observational value must be reported with the experimental error to make sense. Does EPA report how much error there is in their numbers? I am guessing that their measurements and calculations are riddled with huge systematic as well as statistical measurement errors, probably around 10%.

    So, when they say 50 MPG, they probably mean 50 ± 10% MPG = 45–55 MPG.

    10% experimental error would translate as 47–57 MPG overall for Prius and 50–62 MPG overall for Prius Eco. Clearly, this would correspond to a lot of overlap (50–57 MPG overall) between Prius and Prius Eco.
     
    #18 Gokhan, Mar 9, 2016
    Last edited: Mar 9, 2016
  19. Trollbait

    Trollbait It's a D&D thing

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    The manufacturers are the ones doing all the testing. The EPA just double checks a few models.
    Multiple tests are run, and there are rules about averaging them. Hyundai ran into trouble when they used the more favorable results for the average.
     
  20. wjtracy

    wjtracy Senior Member

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    Here we are saying Toyota's "misleading" because actual MPG seems better than EPA 52 avg.
    Refreshing to have THAT problem.
     
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