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Newbie Here; Point me in the right direction?

Discussion in 'Gen 2 Prius Fuel Economy' started by Liberty B, Dec 7, 2021.

  1. Liberty B

    Liberty B New Member

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    I have an '08.
    A bit over 2k miles on it....when I bought it in August of this (2021) year, it was still getting mpg in mid 40's or so.

    The last few tanks of gas have decreased economy quickly, (though it did seem to somewhat gradually trend downward before this,) and I'm now in low 30's.

    Original Battery.

    May or may not be related, but I was surprised awhile back that leaving the headlights on for an hour necessitated a jumpstart (it did jump immediately however.) Not sure if this is normal or not.

    Ive done nothing to the car since owning it, previous owner was good with maintenance tho....and brakes are also still original.

    Decreased mpg and obvious more frequent running of gas engine are the only noticeable changes.

    Where do I start looking for answers?
    Am I safe to most likely assume it is indeed the battery based on this description?

    Thanks!!
     
  2. alftoy

    alftoy Senior Member

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    If you're not mechanically inclined, wait and see if PriusCamper saunters by he may be able to help check the Prius over and do a diagnosis for you. He is based near Portland OR.

    PriusCamper | PriusChat
     
    #2 alftoy, Dec 7, 2021
    Last edited: Dec 7, 2021
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  3. Another

    Another Senior Member

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    Get a good Bluetooth code dongle for $25 and Dr Prius phone app. Run the tests. That’s a first step. The good dongles are listed on the Dr Prius web page.
     
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  4. dig4dirt

    dig4dirt MoonGlow

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    I would recommend testing the 12v battery.
    If you have no clue on the age/state of it, it could cause problems.

    Also checking for current codes is a good thing (y)
    preferred after knowing 12v is good
     
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  5. sam spade 2

    sam spade 2 Senior Member

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    Really ?
    A 13 year old car with only 2,000 miles on it ??

    Gas mileage tends to decrease in cold weather.
    Part of that is unavoidable but tire pressures usually go down which can sap some mileage.

    Your reported symptoms DO sound like early warning signs of a hybrid battery getting weak.......but get your 12 V battery tested first.
    I hope you fully charged it with an external charger after your jump.
    If it is over 5 years old, just replace it.
     
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  6. alftoy

    alftoy Senior Member

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    Sam don't be so gullible, she probably meant 200K.
     
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  7. sam spade 2

    sam spade 2 Senior Member

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    Sure. But we shouldn't have to guess.
    Which is why I was asking.
     
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  8. PriusCamper

    PriusCamper Senior Member

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    Sounds normal... The best MPG you get is going to be when outdoor temps are in the 70's & 80's... But when winter hits and you drive the car on short trips that never take longer than a 1/2 hour the engine barely ever gets up to normal operating temperature to get better than mid to high 30's in MPG. Once you get out on the highway for a long drive you'll see MPG go back up.

    In general, best way to boost MPG is higher tire pressure, as well as using low rolling resistance tires. Just keep adding a pound or two of PSI until traction of tires is not as good and then back off the tire pressure a bit. I've found that 45 psi in front and 43psi in rear is the best MPG vs. Traction ratio in winter.
     
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  9. nancytheprius

    nancytheprius Active Member

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    Does that not trigger tpms light?
     
  10. PriusCamper

    PriusCamper Senior Member

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    never has for me...
     
  11. Liberty B

    Liberty B New Member

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    200K.

    It was the middle of the night when I posted, whoops. o_O
     
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  12. bisco

    bisco cookie crumbler

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    only low pressure
     
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  13. Another

    Another Senior Member

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    wow 45psi, how do you know how high is too high?
     
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  14. alftoy

    alftoy Senior Member

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    Max pressure noted on sidewall. Mine says 44psi.
     
  15. PriusCamper

    PriusCamper Senior Member

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    Interesting... What type of tires? Any chance the pressure is metric, like kilo per square inch instead of pounds per square inch?
     
  16. PriusCamper

    PriusCamper Senior Member

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    Tire traction during acceleration... Soon as they start to slip I back off... That happened to me at just under 50psi.
     
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  17. alftoy

    alftoy Senior Member

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    Michelin X-Tour
     

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  18. Another

    Another Senior Member

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    Famous last words.
    The Michelin specification is max 44psig at a particular weight loading on my defenders too. Max.
     
  19. PriusCamper

    PriusCamper Senior Member

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    Thanks... I didn't know that... I guess Michelin is a bit more honest then other tire makers that for liability reasons won't ever go above 35psi? I now like Michelin better because of that!
     
  20. Salamander_King

    Salamander_King Senior Member

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    +1
    Especially because we know you have drained the 12v battery at least once. Not really sure how the low or dying 12v battery affects the milage, but bizarre things can happen to Prius when the 12v battery is bad. Unfortunately, the AGM battery you have on Gen2 is not very cheap but is much cheaper than the traction battery which is my next guess as to what may be causing the low mileage. The traction battery cost would likely run more than what you paid for the car. If it is still the original battery, then yeah... 200K miles (I am assuming that is what you meant by "2K") is about the mile mark when you may have to replace the traction battery.
     
    #20 Salamander_King, Dec 10, 2021
    Last edited: Dec 10, 2021
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