refuled then reset trip A and B, drove off and they are all different mpg's

Discussion in 'Prius c Fuel Economy' started by priustexasbob, Feb 25, 2018.

  1. priustexasbob

    priustexasbob Member

    Joined:
    Sep 3, 2010
    317
    66
    0
    Location:
    college station
    Vehicle:
    2015 Prius c
    Model:
    Two
    I refuled, I then reset trip A and B before driving off. I circled around from "start" to A then to B and back to start, they all read different. the start and B trip reading were close, about 1 or 2 mpg difference but A trip was off by 5 mpg. I figured they would be pretty much the same reading but why A was so much off was perplexing. I arrived at gym about 5 miles away, the difference from A to B and start was down to 4 mpg. why so much disparity, shouldn't they all not be the same or very close to it?

    I had originally posted this in the 3 forum and had just realized it and copied it here. a mod may delete the one in the 3 forum.
     
  2. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    68,716
    26,930
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    not at all. the only way to get similar readings would be to do the exact same trip, in the same weather, and the same driving conditions.
    almost impossible outside a lab, but you should be able to get within an mpg or two.
     
  3. ztanos

    ztanos All-around Geek!

    Joined:
    Jan 10, 2013
    2,989
    923
    40
    Location:
    Cumming, Georgia
    Vehicle:
    2012 Prius c
    Model:
    Four
    From start is literally that, from when you turn the key. Depending on how long you let the car sit in the place before resetting trip A and B, that could be a good bit of electricity/time. The only way to get all three synched up is to power the car into AUX mode, reset the trips, then power the car on.
     
    William Redoubt likes this.
  4. davids45

    davids45 Member

    Joined:
    Nov 23, 2016
    93
    118
    0
    Location:
    Chatswood, NSW
    Vehicle:
    2016 Prius c
    Model:
    One
    G'day priustexasbob,

    I may not understand your post correctly but.....
    ..did trip A and trip B read the same distance (km or miles)? You re-zeroed them at the same time?

    My understanding is that A and B read/estimate the fuel consumption/mileage for the total A distance and total B distance respectively.
    Only ODO gives a display of just the current trip (or from engines start to engines stop, to be exact), if A and B are not re-zeroed at that trip's start-up.

    So if A km/miles does not equal B km/miles, there is little reason to expect the consumption for A and B to be identical, particularly the bigger the distance difference between A and B for low values of A and B.

    The further I go, the closer A and B consumptions become, but for just a few km/miles, these can be quite different due to the high consumption in the first few km/miles. Local conditions do vary, as does my foot on the accelerator, so I find here that the same short trip can be quite different, especially from a 'cold' start.

    Have you repeated your test several times to reproduce your puzzling result? To come up with a consistent set of averages for A and B?

    Puzzling.

    David S.
     
  5. priustexasbob

    priustexasbob Member

    Joined:
    Sep 3, 2010
    317
    66
    0
    Location:
    college station
    Vehicle:
    2015 Prius c
    Model:
    Two
    yes David, the mileage was exactly the same. I reset (zeroed) everything after starting and within a few seconds I drove away. I will redo this again once I refuel.
     
  6. William Redoubt

    William Redoubt Senior Member

    Joined:
    Feb 13, 2016
    863
    914
    1
    Location:
    Dana Point, CA
    Vehicle:
    2016 Prius
    Model:
    Two
    The calculations provided by the car are estimates only. These are not precision instruments. You have uncovered the fact that the calculations for the two trip meters must not be using the same subroutines to calculate mileage.
     
  7. Mendel Leisk

    Mendel Leisk Lapsed Cargo Cultist

    Joined:
    Oct 17, 2010
    27,246
    16,535
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    It baffled me there, and here, lol. Is there any chance you reword that. I was a draftsman, and then a checker for a few decades, and I pride myself on being able to decipher most anything, but I'm stumped as to what you've done.

    Maybe a diagram??
     
    bisco likes this.
  8. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    68,716
    26,930
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    likewise, i thought it was the fact that i am not detail oriented.
     
  9. Mendel Leisk

    Mendel Leisk Lapsed Cargo Cultist

    Joined:
    Oct 17, 2010
    27,246
    16,535
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    That might actually help...
     
  10. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    68,716
    26,930
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    nope, that's why i tried clarifying testing in both threads. crickets, so far.
     
    Mendel Leisk likes this.
  11. davids45

    davids45 Member

    Joined:
    Nov 23, 2016
    93
    118
    0
    Location:
    Chatswood, NSW
    Vehicle:
    2016 Prius c
    Model:
    One
    G'day pruistexasbob,
    Unless you're keeping a fuel log on A or B (I'm guilty on my B ;) ), you could do a re-test any convenient time by again re-setting your A & B, or even for each coming trip. This would quickly generate more data on this oddity.
    Maybe some others could do the same test on their 'c's and report for a comparison?

    David S.
     
  12. priustexasbob

    priustexasbob Member

    Joined:
    Sep 3, 2010
    317
    66
    0
    Location:
    college station
    Vehicle:
    2015 Prius c
    Model:
    Two
    after 220 miles, they have synced up. I will refuel tomorrow and redo this. sorry for the Kornfusion, math was my strong suit, not English. (diagramming sentences may as well have been done in Klingon as incomprehensible as that was and is to me LOL)
     
    ztanos, Mendel Leisk and bisco like this.
  13. grid

    grid Senior Member

    Joined:
    Aug 22, 2017
    865
    715
    2
    Location:
    BOY
    Vehicle:
    2012 Prius
    Model:
    Four
    Disconnected my 12v battery to do rea/r brake caliper pin relube at the meet up couple weeks ago and driven it everyday. Both trip a and b a/re stillexactly the same, this thread came to mind when I was just about to reset A for an extended trip

    So if you want to truely reset & sync both trips back to 0s, unplug 12v battery and plug it back.
     
  14. Aqua2014owner

    Aqua2014owner New Member

    Joined:
    Mar 22, 2018
    29
    5
    0
    Location:
    Karachi Pakistan
    Vehicle:
    2014 Aqua
    Model:
    N/A
Loading...