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13 mpg

Discussion in 'Wheels & Tires' started by tacotac, Apr 23, 2013.

  1. Apr 23, 2013 at 2:47 PM
    #1
    tacotac

    tacotac [OP] Member

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    Tobie
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    i bought 4 tires Toyo Open Country AT2 size 265/70/17 about a month ago and realised i could only travel 400 km with a full tank, thats about 17.5 L/100km.
    is it just the tire size that's f*(*?ing things up ?
    if it is, how can you calculate the exact mpg ?
     
  2. Apr 23, 2013 at 2:50 PM
    #2
    kryten

    kryten Well-Known Member

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    Check my fuelly stats for comparison. I usually get 15-16mpg city in winter. I did get 13.5 once with lots of idling and -30C.

    In winter, I won't go far past 400km until the light comes on.

    What load range are your tires? PSI? etc.

    Also, when you calculate mpg, you have to account for the size difference. About 3.6% if I'm not mistaken in your case. In reality, you are actually getting a bit better mileage if you did not take that into account. Maybe mid 14's I'm guessing and that is not too much off considering winter gas blend and cold temps still outside.
     
    Last edited: Apr 23, 2013
  3. Apr 23, 2013 at 3:07 PM
    #3
    Mikehole

    Mikehole Well-Known Member

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    TRD Supercharger, Toytec 3" Ultimate Lift w/ 285/75/16s and planning on OBA for sometime in the future. Also thinking about the HWMS and a Warn 8000 for it.
    The tire size f*&ks everything up. I upsized from 265/75/16 to 285/75/16 and that increased the tire size from about 31 to 33 and the weight per tire from in the 30s to in the 50s.
    The increased tire weight isn't like adding 80lbs in the bed. Its much worse. It eats up rotational force to get those fatties moving, so it takes more power to get going and more brake to stop.
    With regards to mpgs, you need to take the new diameter and divide it by the old diameter, and then you will get the percent increase per tire rotation. I normally multiply my total tank miles by that number to calculate true mileage.
    i.e. 33"/31" = 1.06 => 6% increase in circumference (pi x diamter) => 6% further traveled than the gauges think. My tripometer says I went 237 miles on 17.8 gallons (237/17.8=13.3mpg) then I multiply that by 1.06 for the increased distance per tire rotation and get a true mileage of 14.1.
    My mileage is so bad because I've added a s&^t-ton of weight and screwed up my aerodynamics by adding an aftermarket bumper/winch/supercharger and skids. I also frequently carry heavy and bulky loads for work, which doesn't help mpgs.
     
  4. Apr 23, 2013 at 3:15 PM
    #4
    kryten

    kryten Well-Known Member

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  5. Apr 23, 2013 at 3:19 PM
    #5
    teneighty

    teneighty I'd rather be skiing...

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    Seriously?...

    Well you take your mileage and divide it by how much has you use...:confused:
     
  6. Apr 23, 2013 at 3:19 PM
    #6
    tacotac

    tacotac [OP] Member

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    30 psi now
    this winter i had the same mpg but with standard tire size (265/65/17)
    with -20 i think it's normal. But now summer is long gone, 12 degree c at the moment.
    i didn't take the difference of size in my calculation, didn't know how
     
  7. Apr 23, 2013 at 3:22 PM
    #7
    tacotac

    tacotac [OP] Member

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    seriously?
     
  8. Apr 23, 2013 at 3:27 PM
    #8
    Bobbb

    Bobbb "Rumors of Bob, but never Bob. It is Bob, right?"

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    I'm running Toyos in 265/70/17 as well, but the MTs rather than ATs. According to my GPS, when my speedo is reading 65 mph, I'm actually doing 67.5. As I'm primarily highway driving, that 2-1/2 mph difference is what I figure in when doing my usage calcs. Depending on wx, I average between 16-17 mpg normally. Less if I go to town obviously.

    Edit: Also, I'm running 35 psi.
     
    Last edited: Apr 23, 2013
  9. Apr 23, 2013 at 3:30 PM
    #9
    teneighty

    teneighty I'd rather be skiing...

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    Maybe I'm missing something...
     
  10. Apr 23, 2013 at 4:00 PM
    #10
    tacotac

    tacotac [OP] Member

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    thanks man
    if i calculate the way you did it, it only gives me 13 km more on a full tank.
    giving that my tire size is incrased by 3,4%.
     
  11. Apr 23, 2013 at 4:01 PM
    #11
    tacotac

    tacotac [OP] Member

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    that's pretty good mpg
     
  12. Apr 23, 2013 at 4:05 PM
    #12
    Boone

    Boone Vaginas are rad.

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    That's when a junior gets to take advantage of a senior and tell him to read the entire thread before commenting. :stirthepot:
     
  13. Apr 24, 2013 at 5:19 AM
    #13
    teneighty

    teneighty I'd rather be skiing...

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    There is no way this can be accurate... There are to many factors to take into account. And if your getting bad mpg with 265/70 it's your driving habits.
     
  14. Apr 24, 2013 at 5:47 AM
    #14
    jhodge83

    jhodge83 Any dog under 50# is a cat and cats are useless... Staff Member

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    wat?
    it is accurate. i'd usually add the 6% to the mileage, then divide by the gallons used, but it works to the same number. if you read, he's not running 265/70's and also states he has aftermarket bumpers, winch, supercharger, skids, etc that all attribute to the lower mpgs.
     
  15. Apr 24, 2013 at 8:03 AM
    #15
    SickNaban

    SickNaban Well-Known Member

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    i just upgraded to the toyo open country at 2 LT265/75/16 from the stock duflops P245/75/16.....i was getting 21 mpg (mostly highway driving)....i'm now getting between 18-19...not too bad
     
  16. Apr 24, 2013 at 1:38 PM
    #16
    maxpower29

    maxpower29 Well-Known Member

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    stock duncraps are like one of the worst mpg tire I have ever used for that size
     
  17. Apr 24, 2013 at 2:08 PM
    #17
    tacotac

    tacotac [OP] Member

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    i drive within the speed limits ,which is pretty slow, and i'm pretty damn smooth with the pedal. So i can't explain it, but i'm at 14 mpg with 265/70.
     
  18. Apr 24, 2013 at 2:31 PM
    #18
    Desert Drifter

    Desert Drifter Well-Known Member

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    My truck came new with 245-75R16 Dunlop Grand Trek tires which were fair on the pavement but I had a rock poke through the tread the first time I went off-road. I wanted to get something more agressive anyway as the stockers had poor traction in rocks, but had hoped to go at least 10k on the stock wheels and tires.
    So at 3k miles I bought a set of Konig 16x8 wheels because I like the style AND they are light. I put 265/75R16 Dura-Trac tires and my fuel mileage is as good as stock when highway driving. Around town I really dont know as I use my triuck for off-road and getting to off-road stuff only. (Not a daily driver). I think tire/wheel weight is more important that most folks realize. PLUS you may be better with 4.10 or 4.56 gears once you step up the 33" tires (285/75R16 or 285/70R17).

    As for my results I attribute it to keeping the cruise set to 70 mph and the light wheels. Also pump those tires up to 40 PSI to lower the rolling resistance. Max pressure is on the sidewall, don't exceed it even when the tires get hot.
     
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