Bad Gas mileage - 12v battery solution

Discussion in 'Gen 3 Prius Fuel Economy' started by karl.d, Jan 15, 2019.

  1. EricWagner

    EricWagner New Member

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    NewI have been dealing with mileage dropping over the last 4 months. At 100k, I decided to do some maintenance and with the help of NutzaboutBolts, I went ahead and performed:
    1) transmission oil change
    2)engine oil change
    3) spark plug replacement
    4) install oil catch can
    5) removeand clean egr valve amd tube
    6) remove and clean intake manifold
    7) remove and clean throttle body
    8) replaced O2 sensor
    9) replaced MAF sensor

    All of this was proactive maintenance. I had zero issues and no check engine lights.

    After all of this, I experienced a slow decrease in MPG- from normal of 50-54 to 44-47.

    No matter what I did, light on the accelerator, tires at 40psi, premium fuel, ECO Mode, and overall conscious driving g habits, I couldn't get this thing back to "normal."

    Today I decided to bite the bullet and buy a new 12v battery. I had no reason to suspect this was the issue because I purchased this Prius used 2 years ago and when I looked at the battery 2 months ago, the sticker on it said 8/17. I figured the battery is 2 years old- still good right?

    Last week, while sitting in my car watching my in-dash dvd player (which came with the vehicle) a message appeared that I had not seen in the past. I typically sit in my car for an hour or a little more, 3 days a week while my daughter has soccer practice. I'll usually pop a dvd in and watch it.

    The message said something to the effect- shutting down to conserve battery. I am always in Accessory Mode when watching the dvd.

    Today I swapped out the 12v battery with a new yellow top Optima at a cost of approximately $230 dollars at local AutoZone. Drove it right after on the highway for about 10 miles and I'm up over 54!!!

    Hopefully, problem solved
     
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  2. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Stay in Ready to consume electricity, it is much safer.
     
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  3. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    In other words, with the car fully "on", the engine cycling on/off as necessary. Still, doing that won't help the mpg: just switch it right off, bring along a Walkman or similar? Or a book?
     
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  4. RMB

    RMB Senior Member

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    Or cellphone and unlimited data plan LOL
     
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  5. bisco

    bisco cookie crumbler

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    well done! (y) how many miles on her?
     
  6. andreimontreal

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    (silly question, admin delete)
     
    #26 andreimontreal, Dec 19, 2019
    Last edited: Dec 19, 2019
  7. andreimontreal

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    Toyota also told me my battery is in great shape. My mpg not so amazing too. Not sure which battery they were referring to; I always assumed it was the hybrid - now I'm starting to think it was the 12V, not that they were spot on or anything. They gave me this small piece of paper with 4/5 dots full kinda like a tiny receipt.

    Karl thanks for stopping to write details such as the remote not working and whatnot. From what I read around here I might have the same issue.
     
  8. bisco

    bisco cookie crumbler

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    that is definitely a 12v report. is it original?
     
  9. ASRDogman

    ASRDogman Senior Member

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    What type of tires do you have on the car now?
    I will never get the cooper tires again. I'm going back to the Continentals. It's just too hard to get
    the MPG's up. I've lost 5 mpg with the cooper tires.
    For "ME", tire pressure only gained me possibly 1 mpg.

    I seem to remember you asking about tires, did you get new ones yet? If so, which ones did you get?
    That could be where you are loosing the mpg's.

     
  10. andreimontreal

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    I got 4 set of Continental Wintercontact SI Plus about a month ago.
     
  11. ASRDogman

    ASRDogman Senior Member

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    Winter tires... okay. From my understanding of what others have said on Prius Chat, you'll loose the mpg's
    with winter tires. I guess it's how they are designed for the snow. You may have to live with them until summer.


     
  12. andreimontreal

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    Maybe. Time will tell. Gonna check that battery for sure.
     
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  13. ASRDogman

    ASRDogman Senior Member

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    Yep, doesn't hurt to check the battery. Check everything and get everything repaired and up to date.
    Then you eliminate each item and can narrow things down to find a cause to a problem.

     
  14. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    I'm getting better mpg on my 9 year old 15" X-Ice, than my new 17" Primacies...:cry:

    I'm sure it'll level out in a year or two, but just sayin'.
     
    #34 Mendel Leisk, Dec 19, 2019
    Last edited: Dec 19, 2019
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  15. Attila Fekete

    Attila Fekete Junior Member

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    I think the 17” wheel is havier than the 15” - so not only the tyre model, but the wheel size also counts.
     
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  16. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    Yeah definitely, something like 24 pounds vs 16~17? And yeah 17" tires are heavier too. I can feel the difference every time I swap them.
     
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  17. Attila Fekete

    Attila Fekete Junior Member

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    I have my summer tyres on 17” and the winters on 16” - from Prius gen 2, 7 kg / ~15 lbs without the tyre. Summer ones are stored on my attic, I can feel your pain.
     
    #37 Attila Fekete, Dec 24, 2019
    Last edited: Dec 24, 2019
  18. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    I've found a lifting technique that's easy, and easy on the back:

    Bring the wheel/tire up close, oriented roughly correct. Sit on the floor facing it, hook your toes under the wheel at around 5 and 7 o'clock. Lift the wheel with your toes while steadying and guiding it with your hands, onto the lugs. Helps to have good light, so you can see the studs through the wheel holes, line them up.
     
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  19. StarCaller

    StarCaller Senior Member

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    my technique since decades / (y)
     
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