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calculated vs. computer MPG - Please post your results

Discussion in 'Gen 3 Prius Fuel Economy' started by F8L, Jul 10, 2009.

  1. dtuite

    dtuite Silverback

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    Multiply by 0.833 to get Colonial miles per gallon.
     
  2. Analogkid1958

    Analogkid1958 Member

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    I've always seen a two-three mpg discrepancy. How do you folks do your calculated - do you stop the pump at the first click or what - how do you determine you're filling to the same amount each time?

    On a related note - has anyone noticed the fact that the fuel level display goes down a bar or two, then goes back to full? It doesn't seem to be related to incline...

    Thanks!
     
  3. Mr Bill

    Mr Bill Junior Member

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    After 4,500 miles, I find the computer mpg to average around 2.5 mpg higher than my calculated mpg.
     
  4. nolo contendre

    nolo contendre Hybrid Noob

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    My first 3 tanks, all this month were:

    50.5 mpg MID 50.5 mpg Calculated (Dealer Tank)
    53.7 mpg MID 51.1 mpg Calculated
    54.3 mpg MID 52.7 mpg Calculated

    Date of MFG: 02/2010

    I always fill up with 2 pips showing on the guage and I fill one click after the auto shut-off.

    Nolo
     
  5. jdcollins5

    jdcollins5 Senior Member

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    After eight months and 11,000 miles, my displayed mpg averages 3.3 mpg higher than my calculated at the pump mpg. I figure this to be a 7.1% error.
     
  6. tonyl

    tonyl Junior Member

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    20 tanks:
    Computer= 56.6 / Calculated= 54.8
    Best 67.2 @343 miles
    Worst 44.6 78+mph @225 miles
    Hubcaps removed, mud flaps added 3 tanks ago no change in mpg.
     
  7. tunnie

    tunnie New Member

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    2010 Toyota Prius III with Navi

    5,000 miles and about 45 mpg...tried many driving techniques and even 40psi, cant get better gas mileage...
     
  8. mainerinexile

    mainerinexile No longer in exile!

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    Yeah, I've seen the gas gauge go down a pip and then go back up, too. What is that all about?
     
  9. Downrange

    Downrange Active Member

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    First fill-up tonite - indicator said 54.1, got 9 gallons and 468 miles for 52 actual. Salesman said he "filled it up as far as he could" so I did the same, let it trip the auto shut off twice, so I think that's pretty close to as much as it would hold.

    Looks like a 2MPG diff, which seems to be a lot of peoples' experience.

    Built 11/09
     
  10. eldiee

    eldiee Member

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    We have a 2010 V and now have 8500 miles. The computer always reads high. It is between 2-4 mpg higher than actual. Today actual for 512 miles was 53.3 and computer said57.3mpg. Normal is between 2-3 difference. Our average on the computer for 8500 miles is 54.8 mpg. Even with the 2-3 mpg error it still is great mpg. I really don't get to upset with the computer error as long as we average over 50mpg.
     
  11. kithmo

    kithmo Couch Potato

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    how many litres in a US gallon ?
     
  12. Philosophe

    Philosophe 2010 Prius owner

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    A Google search calculation for "1 gal in liter" returns:

     
  13. miogps

    miogps Junior Member

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    I just did the first fill-up. Computer MPG is 54.8 as against 53.7 actual. Driven on local roads with lots of ups and downs. It's mentally challenging to drive Prius especially after my jackrabbit style in a Corolla (1993 manual) that gave 38-40mpg on the same roads. Still drives corolla 3 times a week and Prius 2 times for a daily commute of 46 miles.
     
  14. luger

    luger New Member

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    On my 2010 version 111/IV at 700 Kilos I used 1 tank about 39.xx or for what gas tank it is rated for, can some one tell me my US MPG. Thanks
     
  15. drsbm3

    drsbm3 Junior Member

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    My last three tanks were :
    57.4 MID, 55.02 calculated, 2 Pips at 491 miles
    60.2 MID, 57.25 calculated, 2 Pips at 525 miles
    59.8 MID, 57.59 calculated, 1 Pip at 531 miles

    Overall mileage is 57.06 MID, 54.26 calculated which is a 2.8mpg difference, so 5% variance. I fill 1 additional click after the auto shutoff. So my calculated mpg average is higher than the 50 mpg rating but lower than the optimistic prius computer.
     
  16. Smeerlup

    Smeerlup Junior Member

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    After 5 fillups actual mileage = computer avg for the tank * 0.91 +/- 1%
     
  17. Codyroo

    Codyroo Senior Member

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    If I'm translating what you are asking

    700 km driven
    39 Liters of petroleum used.

    (700 km)*(0.62 miles/1 km) = 434 miles
    (39 liters)*(1 gallon/3.79 liters) = 10.29 gallons

    434 miles/10.29 gallons = 42.2 miles per gallon.
     
  18. alfon

    alfon Senior Member

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    179 miles, 54.8 indicated / 51.8 true.

    Also tank was filled to brim to brim no guess work


    alfon
     
  19. Rebound

    Rebound Senior Member

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    It is NOT good to fill the tank up the neck and to the brim. You should stop filling after one click. The reason is that the emission control systems include [ame="http://en.wikipedia.org/wiki/Onboard_refueling_vapor_recovery"]vapor recovery system[/ame], which routes vapors from your gas tank through a charcoal canister (or similar). If you fill the tank all the way, this vapor line can fill with fuel, soak the canister, and ruin it.

    (Sorry if I sound like a nag, just trying to help)
     
  20. alfon

    alfon Senior Member

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    I did this to get a absolute true reading .

    This is more accurate than the first click at the pump, also I do not do it on a
    regular basis.

    Just for those who have never completely filled their car, after the first click you can get about 2.1 gallons in the tank before it 'brims".

    alfon