Best fuel mileage 18's

Discussion in 'Gen 4 Prius Fuel Economy' started by djarmy2004, Feb 4, 2018.

  1. djarmy2004

    djarmy2004 Junior Member

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    So I had factory 15s and was getting 48mpg average on my prius 4, I drive 78mph most the time to and from work on the highway. well I upgraded to 18s and now get 34. is there a better fuel efficient 18" people have tried or had good luck with. 20180129_105744.jpg

    SM-G955U ?
     
  2. Rmay635703

    Rmay635703 Senior Member

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  3. djarmy2004

    djarmy2004 Junior Member

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    and what makes that 19 so good?

    SM-G955U ?
     
  4. alanclarkeau

    alanclarkeau Senior Member

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    How many tanks have you used with your 18"? I'd do a minimum of 2 full tanks before panicking.
     
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  5. fuzzy1

    fuzzy1 Senior Member

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    When did you change tires? Do remember that MPG falls in winter even without changing tires.

    What actual tire size did you get? Any change in tire diameter will change speedometer and odometer readings, messing up your MPG calculations.
     
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  6. alanclarkeau

    alanclarkeau Senior Member

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    And - you might need to increase the pressure - PRIUS runs fairly high pressures, and if you're running the "recommendation" of the tyre place, they're probably a guess. Add a few more.
     
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  7. djarmy2004

    djarmy2004 Junior Member

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    I'm on my second tank of gas, I will have to look at the tire size, my mph changed by 1. as far as mpg this winter I had been getting 45 and summer I get around 48 to 50. but now im.at 35mpg

    SM-G955U ?
     
  8. padroo

    padroo Senior Member

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    I doubt it that the choice of low rolling resistance tires is that great especially in the size you need.
    I would contact tirerack.com and ask them, they are real good at getting back to you by email.
     
  9. djarmy2004

    djarmy2004 Junior Member

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    thanks padroo

    SM-G955U ?
     
  10. Mendel Leisk

    Mendel Leisk Sand Pounder

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    @djarmy2004 just curious: what are your current 18" tires?
     
  11. padroo

    padroo Senior Member

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    I have a black 2016 and bought wheels that look like yours except they are 15 inch American Racing.

    I haven't installed them yet.
     
  12. djarmy2004

    djarmy2004 Junior Member

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    Falken Ziex 225/40/18 20180204_235434.jpg 20180204_235530.jpg 20180204_235440.jpg

    SM-G955U ?
     
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  13. BLITZ XW50

    BLITZ XW50 Member

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    I'm on 18's and currently getting anywhere from 55-57 mpg per tank fill up. Reseting trip A at every tank to verify. Using Nankang - Noble Sport.
    I check my tire pressure often to make sure it good. Once it drops too much I instantly lose 5-7 mpg easy.
     
  14. Mendel Leisk

    Mendel Leisk Sand Pounder

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    What pressure?
     
  15. BLITZ XW50

    BLITZ XW50 Member

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    Tire pressure usually around 40/42 gets best milleage for me.

    When it dips down close to 35 ish is when I see the mileage start to drop.
     
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  16. padroo

    padroo Senior Member

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    From what I can find the diameter of your tires are slightly larger than the stock tires and they are performance tires and not LRR.

    It's a double whammy for gas mileage and winter. It can't get much better.
     
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  17. alanclarkeau

    alanclarkeau Senior Member

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    Is that by calculation - or a readout from the dashboard?
     
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  18. BLITZ XW50

    BLITZ XW50 Member

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    It's by trip calculations. After fueling I reset the trip meter.
     
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  19. djarmy2004

    djarmy2004 Junior Member

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    what size are your 18s? I will have to raise my tire pressure to 42 front and 40 rear and try that

    SM-G955U ?
     
  20. alanclarkeau

    alanclarkeau Senior Member

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    Because it's calculated by the computer, from a lot of inputs across many many trips, it is only fairly approximate - most people's real calculations (litres/km or whatever) are between 6 and 12% optimistic - every brand of car I've had has been optimistic, funny that.

    With the optimistic error of the trip-calculator, that probably means that 55-57 mpg would be lower.
     
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