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Root cause of poor gas mileage

Discussion in 'Gen 3 Prius Fuel Economy' started by mikeflores2000, Sep 3, 2017.

  1. Prius Maximus

    Prius Maximus Senior Member

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  2. Jaron Lindow

    Jaron Lindow Junior Member

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    Some people put it in the oil too. DON'T! If added to the oil, it can knock sludge deposits loose which can then plug coolant ports and wreck parts of your engine.
     
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  3. Muradali

    Muradali Junior Member

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    Bad mpg
    down to 20
    Also engine is constantly on especially after a sharp drive
    Just had a Catalyser replacement
     
  4. mikeflores2000

    mikeflores2000 Junior Member

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    08-01-2020 update:
    Thanks for everyone’s input.
    Replacing hybrid traction battery improved mpg
    but no where near original 48 mpg when new.
    I don’t plan to clean EGR valve, O2 sensor, replace MAF or spend a thousand dollars not knowing if these repairs will restore mpg.
    Gas consumption
    2020

    7-30 176445 35 mpg 7.3 gallons Costco

    07-21 176187 6.3 gallons mpg 27 Costco

    07-09 176018 8.2 gallons mpg 32 Sinclair

    07-01 175755 4.5 gallons mpg 29 Loves

    06-25 175625 44? MPG 6.23 gallons Costco

    06-16 175510 49 MPG

    06-12-2020 175353 47 MPG
    06-11-2020 replace hybrid traction battery
     
  5. bisco

    bisco cookie crumbler

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    agree, the car is just plum worn out. not worth a major investment. i hope you didn't spend too much on the battery.
     
  6. Grit

    Grit Senior Member

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    o_O
     
  7. mikeflores2000

    mikeflores2000 Junior Member

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    July 5, 2021 update:
    Many thanks to helpful replies. I'm a pretty abusive driver i.e. run over concrete parking wedges, potholes, etc.
    Narrowed down possible cause of low fuel mileage to a dirty Mass Air Flow Sensor given
    my 2010 Toyota Prius purchased new has nearly 190k miles.
    In winter mornings, engine chatters like it is going to fall apart then quiets down after a few seconds
    another symptom linked to dirty MAF sensor. No check engine light and no DTC codes thrown.
    DTC (diagnostic trouble code). Replacing or cleaning may be worthwhile.
    Replacing EGR ( exhaust gas recirculation) valve
    is cost prohibitive.
     
  8. Mendel Leisk

    Mendel Leisk Book Cover Judge

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    Just clean it? Care to DIY? At 190k it’s likely pretty clogged. More info in my signature (bad flywheel).
     
  9. mikeflores2000

    mikeflores2000 Junior Member

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    Where’s bad flywheel?

    I found these on YouTube:

    Intake EGR ports



    EGR pipe cleaning



    Clean out EGR

     
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  10. Mendel Leisk

    Mendel Leisk Book Cover Judge

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    In my signature, a link. If you’re on a phone you need to click avatar to see the signature. Anyway:

    Bad Flywheel | PriusChat
     
  11. mikeflores2000

    mikeflores2000 Junior Member

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    Found them thanks.
    I think I’ll sale my Prius as is.
    I’ll attempt the easy fixes first and
    recheck the mpg.
     
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  12. snowblazer

    snowblazer Junior Member

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    The AC system kills it for me
     
  13. Seanathon

    Seanathon Junior Member

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  14. Seanathon

    Seanathon Junior Member

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    Mike, when you mention that you used 6 bottles of Seafoam, was it the type that you pour in the gas? Or was it the cleaner that you spray into the throttle?
     
  15. mikeflores2000

    mikeflores2000 Junior Member

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    Pour into gas tank.
    Also bought Mass air flow sensor cleaner which
    appears to have eliminated cold morning engine chatter.
     
  16. james nancy

    james nancy Member

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    There are many factors that affect fuel consumption
    External factor
    Tire pressure
    Tyre type
    Gasoline selection, whether the label is appropriate
    Driving style Driving type (mainly cities, mainly highways, how many trips per trip)
    Vehicle load condition (usually a few people in the same group, do you carry heavy objects)
    Local temperature Local road conditions (smooth, a lot of slopes, and frequent water accumulation)
    Internal factors of the vehicle
    Whether the choice of oil is reasonable
    What is the status of the air filter
    What is the condition of egr cooler and valve
    Whether there is deviation in 4 wheel alignment
    Whether the wheel bearing is good
    Whether the brakes are slightly locked
    Whether the high-voltage battery and 12v battery are aging and their performance is degraded
    Whether the front oxygen sensor has clogging and performance deterioration factors
    Whether the injector is dirty and blocked, causing poor atomization
    The spark plug misfires or the ignition energy drops
    Whether the electronic thermostat is normal
    Whether the transmission oil is aging and viscous
    Whether the cylinder pressure is normal (this is unlikely)
    Whether the fuel pump and oil pressure regulator are normal (not likely)
    Whether the amount of refrigerant in the air-conditioning system is appropriate (air-conditioning is often used)
    Whether the data of each sensor is normal (not likely)
    Whether the car body guard is deformed to affect the wind resistance
    Whether the valve timing system is normal (not likely)
    In short, too many factors can affect fuel consumption, and some of them may have obvious effects. If you see here, you may think it is too troublesome to consider so many factors. Please forgive me for being a patient with obsessive-compulsive disorder. I love my car. My purpose is to make me My car is getting better and better. Don't worry, you can do it step by step. You can feel the situation while driving, check and rule out in your free time, and solve them one by one.
     
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  17. mikeflores2000

    mikeflores2000 Junior Member

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    Thanks James. I’ll live with 38 mpg until Prius dies. It will be a backup vehicle or daily driver.
     
  18. Seanathon

    Seanathon Junior Member

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    Did you put in 6 bottles in one tank, or 6 bottles over 6 tanks? Or other? I would like to try this.

    As for me, I ran 1 bottle of Seafoam high mileage at half tank, ran until fill up light. No mpg difference yet :/

    My Prius V is getting 31 mpg, very far from 44 mpg rated when new.
     
  19. mikeflores2000

    mikeflores2000 Junior Member

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    I poured one 16 ounce can of Seafoam per 10 gallon gas tank in 2010 Prius.
     
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  20. Seanathon

    Seanathon Junior Member

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    Thank you!