Change in MPG after Recall

Discussion in 'Gen 2 Prius Fuel Economy' started by mig1980, Aug 15, 2011.

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  1. F8L

    F8L Protecting Habitat & AG Lands

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    Good deal. :)

    Test the 12v battery located in the rear passenger side cubby hole. The battery should read over 12.2 volts. Above 12.4v would be great.
     
    #21 F8L, Aug 16, 2011
  2. mig1980

    mig1980 Junior Member

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    Sounds good. I will report back tomorrow.

    Thank you
     
    #22 mig1980, Aug 16, 2011
  3. uart

    uart Senior Member

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    Ok, good to know that they didn't stuff up the coolant pump change. :)

    Assuming that the dealers aren't deliberately sabotaging cars then inadvertently flattening the 12V battery (and thus leaving it near death) is about the only thing I can think of that would affect MPG's.

    This is another possibility though, one that only effect indicated gas mileage but not your actual MPG. The Prius displayed MPG relies not only on fuel and mileage measurements! It also stores historical data in order to tweak the MPG calculations and make it more accurate. The exact details of this "historical data" I do not know, but I do know that it's reset when the 12V battery is disconnected and this often happens when the Pruis is undergoing any kind of repairs.

    The fact is that many people report changes in their displayed MPG's after the 12V battery is disconnected for a while. Now many people will tell you that it causes the MPG reading increases rather than decreases when this happens, but I think the "historical data" is for tweaking errors in the instantaneous calculation, and depending on which way that error goes, loss of historical can cause an error either way.

    In my particular case I got exactly the type of error that you have. When I first got my Prius from the dealers the MPG display read a good 10MPG less than my "at the pump" calculations. Eventually I found it was due to messed up (or missing) historical data, and over a period of a couple of months it got more and more accurate.
     
    #23 uart, Aug 16, 2011
  4. mig1980

    mig1980 Junior Member

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    Those are some interesting points you are making uart. I will check the battery today. If the batter is good, I will see how many miles I run until next fillup as I was getting about 490 miles on 9 gallons of gas.
     
    #24 mig1980, Aug 16, 2011
  5. mig1980

    mig1980 Junior Member

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    Ok so I checked the battery through an MFD (found a way to read it online). With nothing on the battery reads 12.4v steady. When I push the power button twice (without my foot on the brake) and get the electronics functioning, it reads 12.1v. When I start the car (get it to Ready mode) it reads a steady 13.9v once everything settles.

    I'm guessing the battery is fine??
     
    #25 mig1980, Aug 16, 2011
  6. F8L

    F8L Protecting Habitat & AG Lands

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    Yup, the voltages are within the normal range.
     
    #26 F8L, Aug 16, 2011
  7. mig1980

    mig1980 Junior Member

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    So I haven't had a chance to drive the car much lately but I drove it yesterday and it looks to be slowly getting back to normal. I will run it for a full tank and report back if infact it gives me the same calculated MPG that I was receiving before.
     
    #27 mig1980, Aug 18, 2011
  8. mig1980

    mig1980 Junior Member

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    First of all, I spoke to the service writer about this at Toyota and he claims that the tech didn't even disconnect the battery to perform the pump swap. Here is what I notice. I notice that when I get up to speed and adjust the accelarator, the MPG on the MFD use to go much higher and I would feel some sort of transition as if the car would swicth from engine to battery or something of the sort (almost like a shifting feel). Now I notice that this transition doesn't happen quite as often.

    I also did notice on the energy monitor through the MFD that the battery doesn't stay fully charged. It is mostly in the purple area (two bars down) and very rarely does it creep up to the green. Is this normal as I never checked this before?
     
    #28 mig1980, Aug 23, 2011
  9. 2009Prius

    2009Prius A Wimpy DIYer

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    The HV battery meter should be 4 ~ 6 blue bars most of the time and seldom be purple or green, unless you drive long slopes like in the big mountains.

    I would just drive normally. Observe the HV battery meter. Record each fill up. Compare calculated tank MPG before and after the recall.
     
    #29 2009Prius, Aug 23, 2011
  10. mig1980

    mig1980 Junior Member

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    I don't drive large slopes on my daily commute. I do sometimes but very rarely. Maybe the bars were blue. I noticed them purple but maybe not. I did notice between 4-6 bars on most of the time. Mostly 6. I will continue monitoring my MPG and report back. Haven't had to fill up yet.
     
    #30 mig1980, Aug 23, 2011
  11. richard schumacher

    richard schumacher shortbus driver

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    Hyper sensitization syndrome. After an unusual event (here, the recall service) one notices everything that one didn't before. Perhaps they left the car running for an hour and burned off some gas. Refill the tank and drive it for a week and I'd bet the problem disappears.
     
    #31 richard schumacher, Aug 24, 2011
  12. 2009Prius

    2009Prius A Wimpy DIYer

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    #32 2009Prius, Aug 24, 2011
  13. mig1980

    mig1980 Junior Member

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    I was actually low on gas after I picked up the car so I filled it up within about 2 hours. have been running on the new tank since and I have a habit of reseting the MPG and miles traveled on the MFD everytime I fill up (which I did this time as well) so it is not that.
     
    #33 mig1980, Aug 25, 2011
  14. 2009Prius

    2009Prius A Wimpy DIYer

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    Be patient and collect MPG data for 3 tanks and see if it really dropped from before. Good luck! :)
     
    #34 2009Prius, Aug 25, 2011
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