EPA MPG difference between 2010 and 2011-2015?

Discussion in 'Gen 3 Prius Fuel Economy' started by Unresolved_ERR, Apr 25, 2021.

  1. Unresolved_ERR

    Unresolved_ERR Junior Member

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    Hello all,

    I was on fueleconomy.gov and I noticed that, while the 2010 MY Prius was rated 50 combined MPG, 51/48 City/Highway, all other Gen 3 regular Prius's (non plug-in, non C, non V -- Prii?), were rated for combined 48, with 49/46 City/Highway, with the 2015 sneaking in an extra city MPG (50/46).

    But, the 2012-2015 Prius Plug-in's are all rated for 50 MPG combined, despite the extra battery weight (granted it's not much compared to other plug ins given its short electric range, but nevertheless).

    And, surely the EPA does test each Model Year individually rather than simply saying "hmm looks similar enough" and using the same test results from last year.

    Implying that, 5 times in a row, the car design that got 50 MPG in 2010 got 2 less in the next 5 model years. What's going on here?

    I know there was a somewhat major software update with the 2012+ models (EV indicator even when not in EV mode, a trip summary when you power off the car), which would suggest maybe it was an extra bell or whistle that Toyota put on it, but even the 2011 is only 48 MPG.

    If anyone knows or even has a good guess as to why this is, I'm very curious. Thank you in advance for any response.
     
  2. bisco

    bisco cookie crumbler

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    the epa does not test vehicles regularly. they mostly allow manufacturers to submit their results, hoping that fear of penalty will keep them honest.

    they also change the testing rules from time to time. all in all, it's a poorly done convoluted scheme that perfectly reflects government inefficiency
     
  3. Mendel Leisk

    Mendel Leisk Sand Pounder

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    So the variations (in various non-PIP 3rd gen Prius model years) in mpg ratings are likely just due to evolving test procedures? That’s my hunch.
     
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  4. ChapmanF

    ChapmanF Senior Member

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    Can you grace us with the outlines of how a well-done, straightforward, efficient scheme would look?
     
  5. bisco

    bisco cookie crumbler

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    LOL, if i could, i'd be making a life with the epa. but more importantly, the correct answer to the o/p's question would be most helpful
     
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  6. Grit

    Grit Senior Member

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    I was told by jacktheripper that it is “stupid” to compare MPG results from one vehicle to the other because ymmv.
     
  7. ChapmanF

    ChapmanF Senior Member

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    Well, if you can't, maybe a little lighter hand with the "they're doing it poorly and inefficiently" business wouldn't hurt?
     
  8. bisco

    bisco cookie crumbler

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    don't take it too seriously, it's just a chat :cool:
     
  9. ChapmanF

    ChapmanF Senior Member

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    Sure, but that whole sort of "whatever any regulatory agency does is poorly done, convoluted, and inefficient" trope is so corrosive precisely because places like chats are where it's always getting regurgitated, always with a "don't take it too seriously" as cover.
     
  10. fuzzy1

    fuzzy1 Senior Member

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    That is odd. At some earlier point in time, the 2010 had the same "View Original EPA MPG" link that is attached to the 2015 here, see highlighting below. But it has now vanished.

    Note that if you follow this link on the 2015, it reveals the same original EPA MPG figures still shown on the 2010. Back when the 2010's displayed numbers were downgraded, they matched what is still shown on the 2015.

    Checking around a bit more, I see the 2008-2009 Prius pages also now lack this "View Original EPA MPG" link.

    The EPA has been fiddling with its pages and just which original or later-adjusted scores are displayed.

    upload_2021-4-25_10-43-39.png


    Capture.GIF
     
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  11. Tideland Prius

    Tideland Prius Moderator of the North
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    There was a change to the "roll down" factor around 2013, no? (Either the Fusion Hybrid or the Accord Hybrid had to be retested cause their manufacturer didn't take into account the new equations). There was another minor adjustment in 2016 also (but because the Prius changed generations, the Gen 4 already took into account the new testing)
     
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  12. Mendel Leisk

    Mendel Leisk Sand Pounder

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    FWIW 2015 has the revised pistons and rings (happened sometime in model year 2014), which are higher friction. I’ve noticed on Fuelly to, 2015 has a slight decrease in mpg.
     
  13. Unresolved_ERR

    Unresolved_ERR Junior Member

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    Not that I distrust you, but do you have a source for this?

    Yes, that would make sense - in my original post, I was running by the assumption that, unless otherwise noted (such as when they changed the ratings for 2008+ model years, or 2017+ model years) that the tests are standard, or at least standard enough that you'd only expect small deviations (such as the extra 1 city MPG on the 2015 compared to 2011-2014).

    Yes, for real world results; but the entire point of EPA testing is that it is standardized - the same conditions, and therefore, short of changes to the test itself, should produce at best only slight variations, not a 2 MPG combined difference, at least imo..

    I agree very much. Chats just like here have wonderful information and discussion about niche topic, but there's definitely some ideas about whatever topic it is - even here, about Prius and hybrids in general - that are echo-chambered, and that absolutely can and will be corrosive.

    Thank you fuzzy1 for your concise answer to my original question. With this in mind I did a bit more digging. I wouldn't have expected 2008 test differences to affect 2010 model years (more than a full year between them) but:
    upload_2021-4-25_13-25-28.png
    It seems this, along with the adjustments for MY 2011-2016 to reflect 2017 changes, is the reason. So they are the same car, unsurprisingly, it is just the 2017 testing changes only affecting back to MY 2011. Thank you!
     
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  14. fuzzy1

    fuzzy1 Senior Member

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    Here is an EPA source that:

    How Vehicles Are Tested
    "Fuel economy is measured under controlled conditions in a laboratory using a series of tests specified by federal law. Manufacturers test their own vehicles—usually pre-production prototypes—and report the results to EPA. EPA reviews the results and confirms about 15%–20% of them through their own tests at the National Vehicles and Fuel Emissions Laboratory."

    Which Vehicles Are Tested
    "Manufacturers do not test every new vehicle offered for sale. They are only required to test one representative vehicle—typically a preproduction prototype—for each combination of loaded vehicle weight class, transmission class, and basic engine."

    That later phrase got Ford a knuckle-rapping when they stretched it beyond reasonable modern bounds, and the EPA retested and forced a major ratings downgrade. It is one of the several things contributing to Tideland's memory to back at Post #11.

    That EPA snippet isn't yet the full story, or has been abridged. I'm remembering an intermediate step where all the older models, including 2008-2010, were displaying downgraded numbers on the EPA's Compare Side-by-side page. In fact, I wasn't yet aware that the 2008-2010s were now back to showing their original labels until you pointed it out with this thread.
     
    #14 fuzzy1, Apr 25, 2021
    Last edited: Apr 25, 2021
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  15. fuzzy1

    fuzzy1 Senior Member

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    There was lots more than that. Scroll down to the Ford section of this page for a 'sanitized' description and list of models affected and new vs old numbers. Some revisions were quite substantial:

    Fuel Economy Label Updates

    Numerous other brands were caught on 'problems' too, scroll around that page for the others.
     
    #15 fuzzy1, Apr 25, 2021
    Last edited: Apr 25, 2021
  16. bisco

    bisco cookie crumbler

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    no worries, i am not to be trusted :sneaky:
     
  17. fuzzy1

    fuzzy1 Senior Member

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    ^ ... even when he is right, as he was this time. ;)
     
  18. Grit

    Grit Senior Member

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    :eek::eek::eek::eek::eek::eek::eek::eek::cool::cool::cool::cool::cool::cool::cool::cool:
     
  19. MelonPrius

    MelonPrius Active Member

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    Just in case anyone cares, here's the real world fuelly numbers for the Gen 3 Prius:

    2010: 44.4 mpg
    2011: 44.9 mpg
    2012: 46.0 mpg
    2013: 45.2 mpg
    2014: 45.1 mpg
    2015: 43.6 mpg

    4th Gen: 50+ mpg each MY
     
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  20. BurkPhoto@aol.com

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    I don't have a good reason why that would be, but will note that the EPA numbers have always been BS estimates. My mileage has never come close to EPA ratings. It's closer to Consumer Reports' controlled testing ratings, which I've found to be optimistic.

    In 2008, I bought a 2009 Prius Touring Edition. It averaged 42 REAL* MPG over 176,000 miles. Low was 32 MPG (going 76 MPH for 10 hours on I-95, fully overloaded by 400 pounds, with a roof rack and Sears X-Cargo on it!). High was 46 MPG on a 55 MPH country road in the Fall with HVAC turned off. *REAL means those numbers are calculated manually. And no, I'm not a hyper miler. I drive without regard to saving fuel, and I set the HVAC as needed to remain comfortable. We bought our Prii to save money, not to change our driving habits. (We have six Toyota-built hybrids in our extended family!)

    My 2010 bought used in 2018 gets around 40 REAL MPG average. Low is 38.5 in Winter, and high is 45MPG in summer. The car has 82K on it. Others I know with the same car get maybe 2–3 more MPG. (My son had the exact same 2010 Pack IV for a while, but with standard tires instead of the 17" wheels I have. My sister-in-law had one like that, too, before she got a 2021 RAV4 Hybrid. They got 42-43 real MPG.)

    My son's 2013 Lexus ES300h is rated for 40, but gets 36 REAL MPG.

    We can't complain... But we look forward to BEVs in our future.
     
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