Another Low MPG thread - Yeah I know...

Discussion in 'Gen 2 Prius Fuel Economy' started by Nick Pat, Oct 5, 2015.

  1. Nick Pat

    Nick Pat New Member

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    I have a 2006 Toyota Prius bought used exactly two years ago with 45K miles. Since then I have put another 38K miles on it. It started off by giving me around 48-51 MPG depending upon my driving conditions. Earlier in the summer I realized the mpg started gradually going down. I changed the air filter and it seemed to make some difference. I changed the tires and it did not make any difference. The mpg I was getting was between 36-38 and upon reading some more, I recently changed my 12V battery to the Optima one. I now average 40 mpg which is nowhere near 48 mpg which I was getting before. I change oil every recommended interval so I don't really know the reason behind this drop. My tire pressure is fine, I just got wheel alignment done, it has new air filter, even a new cabin filter, etc.
    My driving habits haven't changed. One more thing is I installed the new battery just this weekend and my 40 mpg measurements are after 175 miles in. Any idea why the mpg dropped? Thanks.
    Oh, I'm not a troll. Misinformed maybe. LOL!
     
    #1 Nick Pat, Oct 5, 2015
    Last edited: Oct 5, 2015
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  2. Daves09prius

    Daves09prius Active Member

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    check the engine oil to make sure it isn't overfilled. - that will affect mpg. The O2 sensors getting old will lower MPG, and the automatic transmission fluid and engine coolant should be changed when possible.
     
  3. Lucifer

    Lucifer Senior Member

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    Cycle the emergency brake to make sure the cable isn't sticking, clean the Maf filter, and yes, the oil gets filled 4/5ths, not full, it actually makes a difference, reset the trip meter after unplugging the 12v for ten minutes.
     
  4. dolj

    dolj Senior Member

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    OP, you didn't mention anything about checking the tire pressures. If they are less than the door placard (35 Front and 33 Rear) this will affect MPG. Running them 3-4 PSI higher than the placard often helps to get even wear across the whole contact patch and has the additional benefit of increasing fuel economy a bit too.

    Hope that helps.
     
  5. bisco

    bisco cookie crumbler

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    welcome! jack up the car and make sure all the wheels spin freely. might need a maf/throttle body cleaning, maybe an injector issue. if none of the above help, could be that your hybrid battery is going south. it's a fairly complicated test, unless you're a good diy'er. all the best!(y)
     
    #5 bisco, Oct 9, 2015
    Last edited: Oct 9, 2015
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