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Possible reasons for 10mpg drop in mileage?

Discussion in 'Gen 3 Prius Main Forum' started by krausternet, Apr 12, 2019.

  1. krausternet

    krausternet Member

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    I have a 2013 level 3 purchased new in 2013. I have about 65K mileage on it. I usually note what type of gas mileage I am getting when I do gas fill-ups. I can't really say exactly when I started to notice the drop in mileage. Maybe about a year ago, back in 2018 at about 55K or 60K I noticed the mileagefrom always getting over 48mpg, and as high as 52mgp, go down to sometimes 42mpg.

    - My driving habits - ratio of freeway to city driving - hasn't changed.
    - I know that tire pressure can effect it a lot and in the years up to when I saw the drop I was aware that I could tweak out at least 2 or 3mpg by inflating the tires higher. So if they were supposed to be 33, I'd go to 36 or 37.
    - I've now taken to inflating the tires to the high 30s to get back to about mileage of 47mpg for the last couple fill-ups, but the ride is pretty hard and noisy.
    - I took the car in for the dealer's standard maintenance during the first years but have not had a real tuneup ever.
    - I do oil changes about every 5K with synthetic oil.
    - I bought tires last year - costco Ecopia EP422+ Grand Touring A/S 195/65R15 91H. I didn't notice a mileage drop when I started using them. I think it came months after that, so I am reluctant to think it is the tires.

    Any thoughts? Should I do a full service? In the old days a change of points and plugs, new air cleaner, setting the valve gap and timing, etc, was important maintenance. Can I expect better mileage with a full service tuneup from the dealer?
     
  2. bisco

    bisco cookie crumbler

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    air and cabin filters?

    there is no such thing as a full service with prius. just follow the factory recommendations in your manual.
    check your oil level and 12 volt battery health.

    clean the hv battery cooling fan and intake grille
     
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  3. KennyGS

    KennyGS Senior Member

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    The only accurate way to track mileage is repeated gas-ups at the same pump over several visits. Using the on-board mpg readout has been not-so accurate for me.
     
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  4. Usle

    Usle Active Member

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  5. krausternet

    krausternet Member

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  6. krausternet

    krausternet Member

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    I am not going buy what the onboard mpg readout says. I simply read the trip odometer and divide that by the gallons on the pump. I tend to fill-up at the same place with the same pump and top it off about the same way.
     
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  7. bisco

    bisco cookie crumbler

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    sounds like a degrading hv battery maybe
     
  8. padroo

    padroo Senior Member

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    Have you cleaned your MAF sensor?
     
  9. hill

    hill High Fiber Member

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    Alignment?
    .
     
  10. Mendel Leisk

    Mendel Leisk Senior Member

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    Yet...

    Also, try a fuel injector cleaner?
     
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  11. ALS

    ALS Active Member

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    Sticking brake caliper?
     
  12. Mendel Leisk

    Mendel Leisk Senior Member

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    Ah. Were rear brakes (in particular serviced recently? Feel all four wheels after a drive, see if any feel hot. The should be slightly warm at most, and uniformly so.
     
  13. krausternet

    krausternet Member

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    I have an OBD2 scanner that I've never used. I finally plugged it in this morning and paired it to my phone and downloaded a scanner app. (Car Scanner ELM OBD2 by 0vZ) Is there some way I could trouble shoot this possible drop in mileage using the scanner? From the huge list of data output what would I be looking for? I imagine there a lot things that could be read.