Mileage on 2008 Prius not what it used to be?

Discussion in 'Gen 2 Prius Fuel Economy' started by BenYL, May 19, 2018.

  1. BenYL

    BenYL New Member

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    When I bought my 2008 Prius ten years ago I really tried to get the best mileage out of it and did pretty well, sometimes getting over 60mpg on a trip. I then forgot about it but have been re-inspired by my 2018 Prius. BUT I just can't seem to get good mileage even when really trying. The motor will run often at a stoplight for example for no reason - battery not low, A/C and heater not on, and it also too often wants to help when I am driving. I rarely see the battery charge due to braking, certainly less than I used to. Otherwise the car at 160K miles sounds great. Does it need some kind of hybrid tune-up or something?
     
  2. Lucifer

    Lucifer Senior Member

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    Call a dealer, order a new Traction battery, 1600$, labor 500$, do a brake job and enjoy five years of 50+mpg’s.
     
  3. bisco

    bisco cookie crumbler

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    have you done all the required maintenance?

    many items in a prius may need service that are not listed in the schedule. you would need to tackle them one at a time.
    check the 12v health.
    ultimately, your hybrid battery may be part of the probem. everything wears out on cars, contributing to lower mpg's over time.
    how are you measuring mpg's, and what are you expecting?
     
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  4. BenYL

    BenYL New Member

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    The small battery died last year but that was replaced. It had its front and rear brakes done recently, is there anything special that has to be done to be sure they don't kick-in too early? The hybrid battery still seems healthy in that it does not discharge to a low level very quickly. There could be other maintenance items I haven't done. I could take it to the dealer for a hybrid-type tune-up but I don't want to spend a lot of money with no effect. I expect that if I give it a good try I should get in the 50s. Also, I expect the gas motor to turn on for no reason and keep running for no apparent reason.
     
  5. bisco

    bisco cookie crumbler

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    a one year old battery can still have a problem. checking it is easy.

    no, nothing has to be done to the brakes, but if you noticed a drop in mileage after the brake job, i would suspect improper installation and brake rubbing.

    the hybrid battery degrades over time, and will provide less assistance before showing you any other signs like the battery charge icon.

    there is no such thing as a hybrid tune up. when you're looking at an old injection, you have to start thinking about injectors, compression, throttle body, maf and etc.

    "also, i expect the gas motor to turn on for no reason and keep running for no apparent reason".

    you do?(n)
     
    len likes this.
  6. len

    len Junior Member

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    There are hybrid shops that claim to do battery conditioning that might help, but you are paying a lot more for that service than you lost in reduced MPG. My 2004 gradually lost MPG over time until the traction battery finally started throwing error codes at 234,000 miles. I was surprised that the "Green Bean" refurbished battery that replaced it increased my mostly highway MPG from 43 to 46. I think that the battery is "pulling it's load" again. Bisco hit the nail on the head - my old battery was contributing less and less to the traction over time.

    There have been people with low mileage 2005s reporting battery failure lately, so battery age seems to contribute more to battery failure than mileage. Your 2008 battery will die at some point. I don't see any reason to invest in it now. Sometime in the next 10 years you will have a decision to make (when it fails).
     
  7. Hoyt Charles

    Hoyt Charles New Member

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    Changed the 12 V battery in my 2008 Prius. Then miles per gallon automatically reset and now I am lucky to get 34 miles per gallon when I was getting 40 miles per gallon before the battery change. I would like to know why this happened
     
    #7 Hoyt Charles, Jun 17, 2018
    Last edited by a moderator: Jun 18, 2018
  8. Steve Roth

    Steve Roth New Member

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    I am sure some of your Hybrid cells are dying or offline. Find a non-dealer Prius repair company and have them checked.
    They can be brought back " online" but will probably fail again and power/mileage falls.
     
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