Slowly losing MPG

Discussion in 'Gen 3 Prius Main Forum' started by Jkan2001, Apr 19, 2018.

  1. Jkan2001

    Jkan2001 Member

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    I bought a used 2010 Prius IV about 10 months ago with 136k miles on it. I changed the oil, spark plugs, air filter, cabin filter, trans fluid, shocks, tested the12V battery and it was doing great getting about 43-46 mpg. After I replaced the OEM michelins with some hankook non LRR tires in the winter the MPG came down to about 41 mpg which was fine by me.

    Now the car is about to hit 150k miles and lately the computer has been reading right at 40 mpg but only getting about 350-360 miles per tank filling up with 1 bar left and 9.5 gallons which is around 37 mpg. The car consumes about a quart of oil every 3,000 miles which from what I understand is somewhat normal for an aging 2010.

    Besides replacing the hybrid battery is there anything that can be done to recover MPG? The car doesn't really need anything as far as a tune up goes to my understanding.
     
  2. sam spade 2

    sam spade 2 Senior Member

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    Test the 12 V battery again.
    If it is over 5 years old, replace it.
    Just because.

    Then don't do anything drastic (expensive) until they stop selling "winter blend" gas.
    Your mileage might go back up a bit.
    Oh, and also check the air in the tires.
     
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  3. bisco

    bisco cookie crumbler

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    maybe injector cleaner, throttle body/maf, egr/intake manifold cleaning.
     
  4. FuelMiser

    FuelMiser Senior Member

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    Asked and answered--it's the tires--go back to decent LRR tires, and keep the pressures up.
     
  5. Raytheeagle

    Raytheeagle Senior Member

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    One thing to consider in the Gen3 is the egr circuit ;).

    At 176 k miles out 2010 just got round #2 of egr cooler replacement and circuit cleaning. I was getting 48 mpg prior to this work:(.

    After the cleaning, I am up over 51 mpg with the same travel pattern back and forth to work:).

    At your mileage, I’d start to think about cleaning the egr circuit for various reasons;).

    Keep us posted (y).
     
  6. farmecologist

    farmecologist Senior Member

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    Yep..your car is at the point where all of this extended maintenance stuff needs to be done.

    Check out the "nutzaboutboltz" maintenance videos here :

    Nutz About Bolts Prius Maintenance Videos | PriusChat

    They have helped many of us tremendously!
     
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  7. Grit

    Grit Senior Member

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    (y)(y)(y)(y)(y)(y)(y)(y)(y)(y)(y)(y)
     
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  8. Jkan2001

    Jkan2001 Member

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    Thanks guys i wish there was a shop or resource that could do the cleaning in dallas. I dont have time to knock it all out.
     
  9. Jkan2001

    Jkan2001 Member

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    Wife driving more conservatively and getting 44 mpg mixed. Still seems a bit low but i can live with that
     
  10. mjoo

    mjoo Senior Member

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    For that you might buy some used motor parts, clean them, and have your mechanic swap the parts. That would be a lot less down time.

    Pixel XL ?
     
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  11. Jkan2001

    Jkan2001 Member

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    Yeah how many hours labor is it to take it all apart and swap the parts? I don’t mind cleaning the gunk just don’t have time to do the mechanical labor.
     
  12. mjoo

    mjoo Senior Member

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    I've only done it once. It took me the majority of two days. But I did extra: installed a screen over the vent duct, spark plugs, changed transmission fluid, etc. An experienced mechanic might take 6-8 hours to swap parts.

    Pixel XL ?
     
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  13. MelonPrius

    MelonPrius Active Member

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    Wow, the estimated price to have a mechanic do the cleaning would be in the neighborhood of 6-8 hours? This is more expensive than I originally thought.
     
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  14. Raytheeagle

    Raytheeagle Senior Member

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    That’s assuming the mechanic will even tackle it;).

    So expect high prices:cool:.
     
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  15. mjoo

    mjoo Senior Member

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    That estimate is just for swapping parts. The removal & replacement of the window cowl is up to 2 hours by itself.

    How much more time will they charge for cleaning parts. Don't know any mechanics that clean. Will they do a thorough job? Or just half a$$ it IDK.

    That's why we try to persuade PCers to clean used parts themselves to avoid engine damage

    Pixel XL ?
     
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  16. The Electric Me

    The Electric Me Go Speed Go!

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    So if what I'm reading is correct, since the baseline of 41 mpg after replacing the tires, the MPG only dropped 1 mpg?

    Well, I think all the maintenance and cleaning suggestions are great. Probably needed in any case. And doing them will probably help raise your MPG's.

    But from reading the post, it seems like the major drop happened after changing to non-LRR tires.
    So I don't know what to advise. Hopefully doing everything else, will raise your MPG to a level you find acceptable. But the biggest drop in your MPG came after replacing the tires.
     
  17. Lucifer

    Lucifer Senior Member

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    So pump the tires up to 45lbs, and....the brakes need service, cleaning and greasing the caliper pins will add mpg's, any bearing noise?
    Trickle charge the 12v so it's charged, make sure the emergency brake isn't at all involved, and replace the cabin air filter.
     
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  18. Mubashir Khan

    Mubashir Khan Junior Member

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    Need to change fuel injectors
     
  19. Borninblue

    Borninblue Active Member

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    You better clean the EGR circuit soon, your mileage drop is your car’s way of telling you it is sick.

    If you fail to clean the circuit you will be wishing you could have your poor mileage back when you see the head gasket repair bill.

    I wouldn’t trust a mechanic to do the cleaning unless they were experienced with Gen 3 EGR problems or replacing with a new EGR cooler. The reality of cleaning the cooler is that it is not something that can be done quickly. You have to soak them, hit them with pressure washer and soak again and again. Search the threads, clogged EGR is the Prius Gen 3 cancer.
     
  20. Mendel Leisk

    Mendel Leisk Senior Member

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    #20 Mendel Leisk, May 1, 2019
    Last edited: May 1, 2019
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