Why my mpg does not match promised values?

Discussion in 'Gen 4 Prius Fuel Economy' started by Go-Green-Pal, Apr 28, 2018.

  1. BurkPhoto@aol.com

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    “Are my figures quite unusual or is it normal? Why am I not getting advertised mpg?”

    Normal. Mileage depends greatly on driving conditions. You will get worse mileage if all you drive is short trips. Driving over 63 MPH/100 KPH will reduce your mileage. Using E10 gas instead of pure gasoline will reduce your mileage. Putting a big car top carrier on a Prius DRASTICALLY reduces mileage because the ICE runs nearly 100% of the time at highway speeds. (We have a Sears Ex-Cargo on Thule roof rails. It costs 10 MPG to drive with it on. It's still cheaper to use than a minivan or an SUV.)

    My wife and I own four Priuses. Our twins drive two of them. My old 2009 Touring Edition (with wide high performance tires) got 42 MPG new, and gets 42 MPG now, after 187,000 miles. My wife’s old 2009 got 46 MPG at 49,000 miles when we bought it used, and gets 46 MPG now, at 167,000 miles. My 2010 Prius 4 got 43 MPG when I bought it used last year with 53,000 miles, and gets 43 MPG now. My sister-in-law has the exact same car I do, and gets about the same mileage. My wife’s 2015 Prius v wagon got 40 MPG when she bought is used at 48,000 miles, and gets 41 MPG now.

    “Does it mean I need to work more on how I drive? Or is this kind of variation between specific cars possible (+/- 5 mpg)? Will it improve on future fill ups?”

    You might be able to learn some pulse and glide techniques that would improve mileage slightly. We just drive, doing whatever the heck we always have. We get what we get, knowing that the ratings are based on conditions we do not encounter. We don’t worry about it.

    The MPG calculator in the Prius is optimistic… anywhere from 1.5 to 3.5 MPG. I always subtract 2 MPG if I want a reasonably honest figure. When I calculate mileage by hand, I average at least five tanks of gas together. That’s because it is very difficult to fill the tank to exactly the same level at every pump.

    TIRES can affect mileage 1-3 MPG, in my experience. I like Ecopia 422+ for mileage. I don’t like their handling. I like Michelins for handling, but their mileage is worse.

    Winter weather reduces mileage a lot, as does Summer driving. When you use HVAC, the car burns more gas to generate more power to run it. Here in the South, ridiculously high humidity forces us to run the AC all the time in Summer.

    Keeping your car in a garage will do wonders for its longevity and its mileage. It won’t have to warm up as much in Winter, and in shade, you won’t cook the battery as much in Summer.

    The worst thing for mileage, though, is NOT getting the car warmed up fully and driving a substantial portion of the time with that warm engine. It burns a lot of gas at startup, just to get the engine warm.

    I used to live in Charlotte, a VERY spread-out city with 750,000 people and a metro area of 2.5 million. I had at least a 30 minute commute to work, which was usually 45 minutes or more in the afternoon. I consistently got 42-44 MPG on that route in my 2009, over a four year period, even with 17 traffic lights.

    Here in High Point, a town of 115,000, almost everything is close to us. So most trips are less than 15 minutes (many are 10 minutes). Mileage falls off when I don’t do anything but drive around town (post office, gas station, grocery store, restaurants and shops).

    Where our Priuses really shine is on long road trips. We nearly always get a couple more MPG on the way to Florida from NC, partly because we take back roads for about 1/3 of the trip, where the speed limit is 55. Traffic jams on I-95 reduce speeds in SC to about 40 MPH on average, so that helps, too.

    I guess what I’m saying, really, is don’t sweat your mileage results too much. They’re really best for comparing car models you might purchase. As a guide to real-world performance, they’re not that accurate.

    The sticker on my 2009 Touring Edition 5 said 60MPG EPA Highway. In my dreams… Consumer Reports' real-world road test said 42. I got 42. I'm happy.
     
  2. fuzzy1

    fuzzy1 Senior Member

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    Do you mean the 2016 change?
     
  3. Prodigyplace

    Prodigyplace Senior Member

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    The EPA ratings changed for 2017. Toyota decided to use the new ones for the 2016 Prius.
     
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  4. Dreamerzcc

    Dreamerzcc Member

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    I have been resetting my trip B meter daily and I have been averaging about 51mpg just to work and back (94 mile round trip). I use to be around 43mpg in heavy stop and go traffic.
     
  5. ETP

    ETP 2019Prius(Limited),Highlander HYB Plat,B52-D,G,F,H

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    Still checking my 2019. But it looks like the MPG gage is fat by 2 MPG. 2016 was very close to actual.
    However the Prius is so superior to my Highlander that I cannot complain. The Highlander is an American engineers nightmare Hodge podge simpson mobile with stuff half arsh done.
    Last Toyota for me that is made in USA.
    The list is too long to put here but yes it is a the Beast from Christmas future that you feel safe in (nick name for the Prius is go-cart).
    Was my last choice for a car (Highlander HYB Plat) but the wife over ruled me.
     
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  6. Prodigyplace

    Prodigyplace Senior Member

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    That reminds me when I worked for a nameless US manufacturer. Their easy way Dir a p,Ian paper copier was to license one from Europe and then redesign to suit their production system and vision. That machine was, among other things, a mix of metric and Imperial sized hardware. A nightmare to repair.
     
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  7. alanclarkeau

    alanclarkeau Senior Member

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    One of my VOLVOs was like that - I think the '73 one (if not the '80 one - if not the '94 one). Get the tool box out, with mostly Metric tools from previous 2 cars, guess at the size - only to find it was an SAE, AF or Whitworth or whatever they used.
     
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  8. ETP

    ETP 2019Prius(Limited),Highlander HYB Plat,B52-D,G,F,H

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    Update on my 2019 Prius! This check was 4.5 MPG short.
    My 2016 Prius was close enough could not pin down where was the error.
     
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  9. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    On my 3rd gen, average error with 163 fill ups tracked: 7.3%. It goes up and down a bit on individual tanks, very likely due to the vagaries of filling up.
     
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  10. ice9

    ice9 Member

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    When I first got my Prius 4 this year, my mpg was pretty bad (about 45 mpg for the first month). Later I discovered that much of this was simply due to sitting in the car with the ac on while trying to figure out how things work. Your average mpg goes to "you-know-what" when you do this. Later I was able to improve fuel efficiency by changing my driving habits. When I hypermile, I get roughly 65 mpg (city or highway). Average driving, I get roughly 55 mpg. However, if I am in anyway in a hurry to get somewhere, all my good driving habits go out the window and my mpg goes to "you-know-what" again.
     
    #150 ice9, Jul 21, 2019
    Last edited: Jul 21, 2019
  11. Lovec1990

    Lovec1990 Junior Member

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    becouse advertised MPGs are ideal conditions as in car load,tyres, temperature and road conditions
     
    #151 Lovec1990, Jul 21, 2019
    Last edited: Jul 21, 2019
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  12. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    In a third gen, with 17" wheels, I wouldn't even entertain sitting with the car running, lol.

    Also 100% gas, no ethanol. It would be with the stock tires, 15" though.
     
  13. ice9

    ice9 Member

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    Couldn't help it. I needed the ac while I was trying to figure out entune and nav. :cool:
     
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  14. Prodigyplace

    Prodigyplace Senior Member

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    I just got about 45 mpg in my Gen 4. 100 F outside with Climate control set to 71. It is all about perspective. I m sure I could have got over the 52 combined value, but it would not have been comfortable.

    There are NO "PROMISED" values, just simulated tests for comparison purposes.
     
  15. ice9

    ice9 Member

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    I keep my ac set to 76ºF. Even when outside temp is a 100ºF, I still average about 55 mpg.

    The trick is to set your ac so that the blower remains low (2 bars), yet still maintains a comfortable temperature. However, when you set your ac up this way, you might find that sometimes a pocket of hot air will form near your head/face - it eventually dissipates as air in the cabin circulates. In any case, this should still keep you cool enough so that you don't break out in a sweat. Also, this usually doesn't work when you have passengers, because air flow inside the cabin isn't uniform and people rarely have the same comfort level.
     
  16. fuzzy1

    fuzzy1 Senior Member

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    Actually the ideal conditions ratings are the much higher CAFE numbers, not the EPA numbers. Back in the 1970s, they were the same scale. But they were a bit unrealistic or atypical even then -- engine pre-warmed, no hot or cold weather, no A/C, and the national 55 mph speed limit was in force -- so EPA started marking them by applying 'fudge factor' corrections to get ratings more in line with people's real-world results.

    But each time the EPA 'fixed' the scale by changing the fudge factors and adding additional tests reflecting harsher conditions, ordinary consumer results kept getting knocked down again through increased congestion, increased speed limits and reduced enforcement, and continued horsepower wars allowing more aggressive acceleration and bad fuel economy habits. These changes them demanded even more EPA scale changes. The cycle continues.

    However, under really ideal conditions, you can still achieve that much higher CAFE number, which is still used for continuity for the required fleet MPG requirements and reports. But 60+mph speeds don't qualify as ideal.
    Exactly. No promises, "Your mileage may (actually will) vary", this reference number is the government-mandated number from the government-mandated tests, and is the only number they are legally allowed to advertise.
     
    #156 fuzzy1, Jul 22, 2019
    Last edited: Jul 22, 2019
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  17. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    In Canada the dealerships love to advertise the highway component (typically better with a gas-only vehicle). Also, even though the country switched to metric gas measurement maybe 40 years back, they often express the fuel economy in miles per imperial gallon, which is something like 20% more than a US gallon.
     
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  18. jb in NE

    jb in NE Senior Member

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    This is a bit of a stretch. Continued horsepower wars allowing more a
    Even with increased horsepower, the EPA test was conducted on that vehicle. Aggressive acceleration and bad fuel economy habits are not a result of anything other than the right foot of the driver.
     
  19. Mendel Leisk

    Mendel Leisk Titanic Social Director

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    A car that looks like a street dragster is hard to drive conservatively though, lol.

    At the risk of wandering into FHOP, isn't it funny how conservative and conservationist are at loggerheads?
     
  20. jb in NE

    jb in NE Senior Member

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    They aren't. I know conservatives who are conservationists, and on the other hand know liberals who are not.

    My son drives his Gen2 Prius like he stole it, with no regard for efficiency. It still gets better mileage than his Jeep or his wife's 400+ HP BMW, but when I drive his Prius I get at least 20% higher mileage.
     
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