1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Warnning: MPG gauge meter is inaccurate for all prius

Discussion in 'Prius c Fuel Economy' started by NewYorkan, Feb 26, 2014.

  1. Mendel Leisk

    Mendel Leisk Senior Member

    Joined:
    Oct 17, 2010
    54,470
    38,103
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    Yup, so your first calc will be off a little, to one side. And the next will be off to the other way, cancelling out.

    Say on your first fill up you got the tank a little fuller than usual, and this is reflected in your calc, "dropping" your mpg. With your next fill up, it'll take less than usual at fillup, "improving" the mpg. And by now your running average will be pretty deadly. And these variations are small to begin with. The longer you record distance travelled and gas consumed, the less anything can budge it.
     
    xraydoug likes this.
  2. ztanos

    ztanos All-around Geek!

    Joined:
    Jan 10, 2013
    3,339
    1,149
    40
    Location:
    Cumming, Georgia
    Vehicle:
    2012 Prius c
    Model:
    Four
    It might be negligible, but that doesn't change the fact that it's still there. I understand that it's there and use fuelly as well (love it). But I understand that these things are all outside of my realm of control. I deal with it and move along. I was just pointing out that they are there and that the computer might not be as inaccurate as everyone thinks.
     
  3. ztanos

    ztanos All-around Geek!

    Joined:
    Jan 10, 2013
    3,339
    1,149
    40
    Location:
    Cumming, Georgia
    Vehicle:
    2012 Prius c
    Model:
    Four
    If pump a puts in 5.5 gallons out of 6 and pump b puts in 5.3 out of 6... I can't just "assume" that they will cancel out. They will be close, I'm not disputing that. I'm just saying that there will still be variation.
     
  4. xraydoug

    xraydoug Active Member

    Joined:
    Sep 14, 2013
    571
    176
    0
    Location:
    Roseburg, Oregon
    Vehicle:
    2013 Prius c
    Model:
    Two
    Why would I need to find an excuse for an inaccurate meter? I am smart enough to believe that with today's technology Toyota could install a computer to alter the mpg readings by 1% or whatever they wanted. In fact it would be easy enough for them to put one in that the driver could adjust under settings. I think it is stupid to think otherwise, and if I want to complain about it I will.(n)
     
  5. ewaboy

    ewaboy Active Member

    Joined:
    Feb 18, 2012
    693
    205
    0
    Location:
    Hawaii
    Vehicle:
    2012 Prius c
    Model:
    Two
    I just minus the 3+ mpg off what the meter shows while driving - it's automatic by now.

    Fuelly tells me what I need to know for the record.

    YMMV
     
    ztanos likes this.
  6. NewYorkan

    NewYorkan Junior Member

    Joined:
    Jan 27, 2014
    64
    12
    0
    Vehicle:
    2013 Prius c
    Model:
    Four
    If I don't know anything. I will ask and I learn.
    If I am wrong. I admitted and then I learn.
    If I don't agree on something, then I do research before make an A$$ of out myself.
    In this thread clearly said that the METER is inacurrate. There are 2 type of people reacted negatively to this fact. The 1st type are the one who blindly love the C. If anyone said a bad thing about the C, they will react negatively. I love my C very much too. But I still keep my fact straight.
    The 2nd type are the one missed read the topic. This is about the METER. Not MPG of the C. Their big mistake is trying to improve MPG. It won't change the METER problem. The higher the MPG, the more error in the METER. When my meter said I'm driving 50 MPG, but I'm doing only 47.5 MPG. It just irritate the heck out of me. It won't bother me if I don't use the meter, but I do use it all the time.
     
  7. ztanos

    ztanos All-around Geek!

    Joined:
    Jan 10, 2013
    3,339
    1,149
    40
    Location:
    Cumming, Georgia
    Vehicle:
    2012 Prius c
    Model:
    Four
    Can the C be improved? Absolutely. What car can't?
    I must have missed those in the 2nd group. But then it's been a while since I went back and re-read all 4 pages.
     
  8. NewYorkan

    NewYorkan Junior Member

    Joined:
    Jan 27, 2014
    64
    12
    0
    Vehicle:
    2013 Prius c
    Model:
    Four
    No, I didn't mean you. I meant those who blame for tire pressure or gas stations. Doesn't matter what pressure the tire or where you filled you gas or what kind stuff you in gas tank, the METER still show higher than the actual.
     
    xraydoug likes this.
  9. ztanos

    ztanos All-around Geek!

    Joined:
    Jan 10, 2013
    3,339
    1,149
    40
    Location:
    Cumming, Georgia
    Vehicle:
    2012 Prius c
    Model:
    Four
    The meter and fuel nozzles at stations can affect the gauge, though. It won't be extreme and someone who isn't doing experiment level notations will never notice it, but it's still there.
     
  10. xraydoug

    xraydoug Active Member

    Joined:
    Sep 14, 2013
    571
    176
    0
    Location:
    Roseburg, Oregon
    Vehicle:
    2013 Prius c
    Model:
    Two
    I agree the meter is set wrong. and that must be intentional from toyota.
     
  11. NewYorkan

    NewYorkan Junior Member

    Joined:
    Jan 27, 2014
    64
    12
    0
    Vehicle:
    2013 Prius c
    Model:
    Four
    Actually, it affects the actual volume of gas in the tank, not the meter. But the nozzles variation from different gas stations turned out be very close to each other. I filled from 3 different gas stations, and my meter constantly showed 5% higher than tank calculation. Their nozzles look very different from each other too, I was expecting about 0.1 gal different in volume of the gas, but suprisingly the gas volume are very close to each other. I never add any extra gas after the pump stops.
     
  12. ztanos

    ztanos All-around Geek!

    Joined:
    Jan 10, 2013
    3,339
    1,149
    40
    Location:
    Cumming, Georgia
    Vehicle:
    2012 Prius c
    Model:
    Four
    Since the meter reads how much fuel is being burned... from the tank... it does have a correlation. Just like all of the others that I mentioned, but whatever the cause, they do still all add up to the meter being wrong and that shouldn't happen with today's tech.
     
  13. NewYorkan

    NewYorkan Junior Member

    Joined:
    Jan 27, 2014
    64
    12
    0
    Vehicle:
    2013 Prius c
    Model:
    Four
    Yup, but here are the reason I'm so upset about it.
    1. This problem is known for long time, at least since 2007 (not to public, but to car company and technical people).
    2. Not only Toyota, but all the car industrial doing this on PURPOSE. If it was a mistake, it won't bother me. But doing it on purposely is just really annoying. Especially, it fooled me until I look it up.
    3. It is easy fix. All the calculation all ready been done. All they have to do is take the number and time .95. Maybe a little more than this, but nothing like sending someone to the moon.
    4. Toyota in general is good company. The prius is extremely good car. I just don't see the benefit of lying to people. Sadly, they followed the car industrial to showed lousy 5% higher than actual.
     
  14. ztanos

    ztanos All-around Geek!

    Joined:
    Jan 10, 2013
    3,339
    1,149
    40
    Location:
    Cumming, Georgia
    Vehicle:
    2012 Prius c
    Model:
    Four
    5% on a 50mpg car is the only reason you notice it. They probably* wrote the code on their first gauge (which would have been around a 25mpg car or even less. At 25mpg you are looking at the car telling you that you are at 25 when you are really at 24. They probably* figured that it was close enough and worked, so why fix it.

    *probably is being used because I don't work for Toyota, I just use the logic that if they wanted to lie about something, they would do it like Ford did and lie completely. The car gets what the EPA test says it will (which is what Toyota says the car will do)... and then some, in most cases.
     
  15. Easy Rider

    Easy Rider Active Member

    Joined:
    Feb 9, 2014
    982
    210
    0
    Location:
    N. Central Florida
    Vehicle:
    2013 Prius c
    Model:
    Three
    And now you KNOW what the fudge factor IS and yet you still ALLOW it to upset you.
    That is YOUR problem; not a problem with the car or with Toyota.
    YOU just need to get over it and move on.......to something that is really important.
     
    mtbiker53 likes this.
  16. miscrms

    miscrms Plug Envious Member

    Joined:
    Aug 21, 2007
    2,076
    523
    5
    Location:
    Phoenix, AZ
    Vehicle:
    2005 Prius
    Frankly, if this is the greatest tragedy in your life I hope you count yourself very blessed.
     
    Mark323, mtbiker53 and ztanos like this.
  17. moltenmetal

    moltenmetal Junior Member

    Joined:
    Aug 25, 2008
    15
    0
    0
    Location:
    Toronto, Ontario Canada
    Vehicle:
    2008 Prius
    My 2013 Prius C has shown a consistent deviation between the displayed fuel economy and the fuel economy measured by mileage and fuel volume. Summer through fall, the two match very well. In WINTER, the deviation correlates with temperature: the colder it gets, the more the display over-estimates the actual fuel economy.

    Maximum deviation during the coldest months was about 10%.

    Fuel dispensed at the fuel pump is measured by a "for trade" traceable measurement device corrected to 15 C, here in Canada at least. And unlike my 2008 base model Prius, there is no tank bladder to confuse fill-up to fill-up economy checking by introducing a variable tank volume to "full". My 2008 averaged 5.77 L/100 km over 190,000 km, start to finish, and my 2013 Prius C is doing better than that, so I'm not concerned. Just curious about what might be causing the deviation that increases as the ambient temperature drops. It's not fuel density, as that would work in the other direction. It's not air density or temperature because air mass flow is measured by means of an actual massflow measurement device in the engine. Very curious what the issue might be...it is definitely there.
     
  18. ztanos

    ztanos All-around Geek!

    Joined:
    Jan 10, 2013
    3,339
    1,149
    40
    Location:
    Cumming, Georgia
    Vehicle:
    2012 Prius c
    Model:
    Four
    You're the first one I've read about that is having a temperature based variation. The rest have been consistently 3-5% off.
     
  19. xraydoug

    xraydoug Active Member

    Joined:
    Sep 14, 2013
    571
    176
    0
    Location:
    Roseburg, Oregon
    Vehicle:
    2013 Prius c
    Model:
    Two
    mine is less than 2% off over the lifetime. Thats less than 1 mpg off getting over 50 mpg calculated at the pump.
     
    ztanos likes this.
  20. ztanos

    ztanos All-around Geek!

    Joined:
    Jan 10, 2013
    3,339
    1,149
    40
    Location:
    Cumming, Georgia
    Vehicle:
    2012 Prius c
    Model:
    Four
    That's excellent. But it's consistent right?