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Gen 3 with 195,000 miles and falling MPG...

Discussion in 'Gen 3 Prius Main Forum' started by TheHorsts, May 20, 2018.

  1. TheHorsts

    TheHorsts Junior Member

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    Oakland, CA
    Vehicle:
    2010 Prius
    Model:
    IV
    We've got a Gen 3 Prius with 195,000 miles and the MPG are falling rather dramatically.

    We live in a hilly part of the Bay Area and have typically gotten about 42-44 mpg "around town", which fell to about 40 mpg, and now is down to about 38 mpg.

    There are no error codes whatsoever.

    One definite symptom is that it seems to kick on the gas engine more than it used to. On flat roads, a warmed up engine, and a charged traction battery, when starting from a stop light with even a light touch on the accelerator it often seems to kick on the gas engine. We don't seem to remember is doing this as much.

    Any ideas?

    Local Toyota service says the hybrid battery may need replacing, but they don't want to recommend that until there are error codes that finger the battery.

    Thanks!
     
    #1 TheHorsts, May 20, 2018
  2. BZzap!

    BZzap! Senior Member

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    The symptoms sure do point towards traction battery decline. I’m surprised the dealer hasn’t run a voltage test to determine the battery condition. Guessing is just guessing.
     
    #2 BZzap!, May 20, 2018
    padroo likes this.
  3. Raytheeagle

    Raytheeagle Senior Member

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    Prime Plus
    Can you provide us with some additional details ;):

    • How long has the mileage been declining?
    • Have you gotten dealer service or done any maintenance yourself?
    • How fast does your battery cycle between full and empty?
    Keep us posted (y).
     
    #3 Raytheeagle, May 20, 2018
  4. Mendel Leisk

    Mendel Leisk Senior Member

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    They can hook up Techstream and do a "hybrid health check" I think, it tests the battery, reports the voltage or whatever for the individual cells, makes an assessment.

    With that sort of mileage, and regularly driving in hilly condtions, can be tough on the battery.
     
    #4 Mendel Leisk, May 20, 2018
  5. TheHorsts

    TheHorsts Junior Member

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    Vehicle:
    2010 Prius
    Model:
    IV
    The most recent drop has been rather quick. In about the last 15,000 miles or so, it's declined by about 3-4 mpg.

    All the major service has been the dealer. I change oil and filters myself.

    The traction battery seems to deplete and recharge rather quickly. From our house to the bottom of the hill is about a mile. If I coast down the hill while slightly engaging the regenerative braking, it can take the traction battery from 2 bars to almost full -- maybe two bars from the top.
     
    #5 TheHorsts, May 20, 2018
    Raytheeagle likes this.
  6. Raytheeagle

    Raytheeagle Senior Member

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    2019 Prius Prime
    Model:
    Prime Plus
    Since you do all the oil changes, you are somewhat diy inclined it sounds :).

    Some items to consider:

    • Had the egr circuit been cleaned to remove carbon deposits?
    • Does your Prius consume any oil?
    • Have you thought about maintaining your hv battery before it fails?
    • When were you thinking of doing the spark plugs?
    While the hv battery sounds like it is getting weak, other factors don’t help it out:(.

    Keep us posted (y).
     
    #6 Raytheeagle, May 20, 2018
  7. TheHorsts

    TheHorsts Junior Member

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    IV
    1) I have not had the EGR circuit cleaned. Likely, it is full of deposits.

    2) It's been consuming oil. I'm now up to about 1 qt every 2500 miles. I'm considering moving to higher weight oil (0w-30 or 5w-30 Mobile 1) once I get through the 0w-20 we still have.

    3) By "maintaining" do you mean replacing individual cells? My reading about that seems to say that once you start changing individual cells, that it just keeps needing periodic cell replacement. Looking at the videos, it's seems like a rather involved. I'm not sure how many times I'd want to do that. If we just install a whole new battery and get another ~200,000 miles, I would be happy.

    4) Spark plugs have already been replaced. It was either at 125,000 miles or 150,000. I'd have to check the records.
     
    #7 TheHorsts, May 20, 2018
    Bay Stater, Mendel Leisk and Raytheeagle like this.
  8. Raytheeagle

    Raytheeagle Senior Member

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    Cleaning the egr circuit will have several benefits. I’d look into doing it;).

    I’ve been running 5w-30 for 60 k miles now, and has helped our oil consumption go from a quart every 4 k miles or so to a quart every 5 k miles. While that doesn’t seem that great, this is while the engine had higher mileage, so I’m happy:).

    Hybrid Automotive makes the prolong battery maintenance equipment, and I have installed a harness in our 2010 with 179 k miles on It. The equipment has helped keep it hybrid battery in good shape ;).

    I just did a egr circuit cleaning and while I had the windshield wiper cowling off, I changed the plugs out. Something to consider as you lol into your egr circuit :).

    Good luck and keep us posted (y).
     
    #8 Raytheeagle, May 20, 2018
    Mendel Leisk likes this.
  9. ensoniqman

    ensoniqman Junior Member

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    Vehicle:
    2007 Prius
    Model:
    Two
    I lived in the hilly areas of Lake and Napa county. Ours finally started to lose MPG when the head gasket was going out. Previously, the o2 Sensor and fuel ratio sensor made a difference in MPG loss. I changed those & the MPG improved. And winter time gas always gave us lower MPG no matter what.
     
    #9 ensoniqman, May 25, 2018
  10. Bgustafson

    Bgustafson Active Member

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    Persona
    With 195k and no EGR cleaning I'd be concerned it's something worse than the hybrid battery.... get that cleaned ASAP!. (y)

    If you can get Techstream working, it'll save you some $$ for a battery check. Dealer will charge you $69 for a "battery health check" lol

    ...but I still haven't gotten Techstream working on my laptop. Arg.
     
    #10 Bgustafson, May 25, 2018
    Raytheeagle likes this.
  11. Raytheeagle

    Raytheeagle Senior Member

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    Prime Plus
    What version are you trying to install :whistle:?

    What troubleshooting have you done to get it going?

    Keep us posted (y).
     
    #11 Raytheeagle, May 25, 2018
  12. Keepdriving

    Keepdriving Junior Member

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    Yeah, 195k is when I first got my check hybrid system light come on. I’m at 215k now and my battery also loses and recharges just as quickly. I seem to coast more than before so my mileage is still similar to before but then where I am, the roads are terrible but mostly flat.
     
    #12 Keepdriving, May 25, 2018
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