Extremely Bad Gas Mileage

Discussion in 'Gen 2 Prius Fuel Economy' started by MaddieS, Nov 7, 2018.

  1. MaddieS

    MaddieS New Member

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    Hi all! I’ve solved a lot of my Prius problems through this chat so I decided to reach out. I have a 2007 Prius that was bought new. It reached 200,000 miles a few weeks ago and I started getting only around 250 miles per tank, a full tank would take about 8 or 9 gallons. I’m now at 205,000 miles and I’m only getting 160 miles per tank. It’s still telling me that I’m receiving 45 miles per gallon but I don’t believe that’s true. My tire pressure is fine and I’ve kept up to date on all of the needed replacements etc. Has this happened to anyone?
     
  2. Tideland Prius

    Tideland Prius Moderator of the North
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    The rubber bladder inside the fuel tank is notorious for varying the tank size (and shrink as it ages); although 160 miles is really low and can't all be explained by the bladder.

    Did you recently have an oil change? Check to see that the oil level is correct and not overfilled.

    Check the engine air filter, maybe it's dirty, resulting in low airflow and poor fuel-air mixture.
     
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  3. TMR-JWAP

    TMR-JWAP Senior Member

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    The mpg displayed by the car is calculated using fuel curves/pressure/injector duration/all those fancy things floating around in the ECU/etc. Considering the car's electronics are still showing normal mpg, yet actual miles per tank are extremely low (yet fill volume is normal........I would focus some attention on looking for a fuel leak.

    Know what I mean? The engine IS getting 45 mpg, it's just that only half of the gas in the tank is going to the engine. The rest is going onto the ground or into the air.......maybe....
     
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  4. bisco

    bisco cookie crumbler

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    fill the tank, reset the trip meter, drive until the last pip, refill and divide miles by gallons pumped and report back
     
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  5. jerrymildred

    jerrymildred Senior Member

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    There ya go, gettin' all logical. Again. :D

    I have to agree with this. If the car says it's getting 45 mpg, then that's what the engine is getting. Well, almost 45 anyway. If you're putting 8-9 gallons in the tank to go 160 miles, then obviously, most of the gas isn't reaching the engine. I would think that that would cause a big stink. Literally.
     
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  6. TMR-JWAP

    TMR-JWAP Senior Member

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    Maddie????

    Hope you were able to resolve the problem. Yes or no, please let us know. The more feedback that gets posted, the better our "well of knowledge" becomes.
     
  7. douglasjre

    douglasjre Active Member

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    Those don't effect fuel economy.
     
  8. Tideland Prius

    Tideland Prius Moderator of the North
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    A dirty air filter would (Edit: No it doesn't) . But the shrinking bladder won't (but could be one of the contributors to the lower range)
     
    #8 Tideland Prius, Nov 13, 2018 at 11:19 PM
    Last edited: Nov 14, 2018 at 1:23 AM
  9. padroo

    padroo Senior Member

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    Those Gen 2 gas tank bladders got you by reducing the amount of fuel you can put in the tank and on top of that cold weather makes it seem much worse than it is.
     
  10. douglasjre

    douglasjre Active Member

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    I'm sorry tideland, a dirty air filter does not effect fuel economy. To be politically correct is to not correct you so I'm not going to be politically correct but I'm also not going to put it in a lot of time trying to teach you this one. You're going to have to teach this one to yourself I'm sorry. the same token that cannot let you propagate false information as though it were correct just because it is your belief system.

    I'm an ase-certified mechanic and a practice medicine now because I went to school for a long time so I didn't have to be a mechanic anymore. You need to learn what a mass airflow sensor is. You need to learn how the system adjusts to the amount of air that goes through so that the fuel ratio remains constant no matter how dirty and air filter is. an oxygen sensor monitors to confirm that the fuel ratio is stoichiometric. The mass airflow sensor recognizes the correct amount of air flow even if the throttle vane is wide open but the air filter is kind of dirty.
     
    #10 douglasjre, Nov 14, 2018 at 12:47 AM
    Last edited: Nov 14, 2018 at 12:53 AM
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  11. douglasjre

    douglasjre Active Member

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    Unsubscribed from this topic because I don't feel I'm learning anything here.
     
  12. Tideland Prius

    Tideland Prius Moderator of the North
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    Roger that. Sorry :( I will go pick up a book (well I guess a digital book).
     
  13. jerrymildred

    jerrymildred Senior Member

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    Poor @MaddieS! I think you guys ran her off. I wonder if she's still only getting 160 miles on 8 or 9 gallons of gas. Remember the original question?

    I hope she comes back, because with enough info, there's a good chance someone like @TMR-JWAP can point her in the right direction.
     
  14. douglasjre

    douglasjre Active Member

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    You're right about that. I've found diagnostic suggestions don't often get result in success when done by text messages. The person with hands on the problem needs to be armed with knowledge plus tools plus wisdom and much of that comes from experience. As listeners we attempt to guide the diagnostics but it doesn't always help unfortunately.

    most of all after somebody has solved the problem they don't follow up and give us the answer to what they discovered. There's often no closure. This is where we all can benefit from this discourse but many times do not. Hopefully she does respond so that we can add this causative agent as a differential for the next person who has a similar problem.
     
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