13 Speed Fuel Mileage

Discussion in 'Experienced Truckers' Advice' started by TigerShark, Feb 20, 2017.

  1. TigerShark

    TigerShark Medium Load Member

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    2014 T660 13speed EF.
    I'm getting about 5.5 loaded @40000
    Running anywhere from 65-80.
    Would running @ 63 in "12 direct" (Guessing on knob would show 8L)
    Be best for fuel mileage?
     
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  3. STexan

    STexan Road Train Member

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    You're joking, right? You're serious? ... 65-80? Oh dear.

    No, running in 12 is not going to help your mileage in that case. I heard a wild rumor one time years ago that running slower (55-65mph), improved range and reduced fuel costs considerable versus running 75 and 80 mph.

    I get 7.2-7.4 doing 65mph, always at least 70k-80k and running 48 states and a lot of northwest. No, I'm not passing everyone on the road and I realize that may be a problem for some. For those, they are going to have to decide where their priorities are ... Passing lots of trucks or passing lots of fuel pumps. You simply can't have it both ways. Sorry.
     
    Last edited: Feb 20, 2017
  4. Mullet_Head87

    Mullet_Head87 Medium Load Member

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    6.7 - 7.0 fully loaded @ 65...or really 64.8mph 2016 freightliner Cascadia auto.
     
  5. Heritage11

    Heritage11 Light Load Member

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    My numbers are comparable in a '16 T680 / 13speed running 65 at heavier weights eastern half of the country.

    If I get a string of lighter loads ( under 30k ) I can easily average 7.8 at 65

    To see any benefit from dropping it to 12 I'd have to run 55-57
     
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  6. TigerShark

    TigerShark Medium Load Member

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    Yeah 80 or 85 depends on which cattle haulers I can sneak in with.
     
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  7. Toomanybikes

    Toomanybikes Road Train Member

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    Their is never any fuel economy benefit to running a gear down. OP is mistaking the transmission efficiency loss associated with OD vs direct drive gear, with truck efficiency. Transmission efficiency is just part of the equation:A very small part. You wan't better over all efficiency you need to spec the truck differently.

    Keep in mind: Less speed will always increase efficiency. And when your talking fuel efficiency numbers always consider the source. A lot of fools trust the lie-a-lot-meter built into their truck. Numbers in the real world are always much lower. Much more like yours already.
     
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  8. TigerShark

    TigerShark Medium Load Member

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    Thanks that's all I was wondering.
     
  9. Heritage11

    Heritage11 Light Load Member

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    That's very true and something most company drivers don't bother to track because they're either too lazy or don't care or both. The company always thinks we're doing better than we are. I track both to the tank and what the box says and the variance per trip. It can be as little as .2 to as much as 1.8 but always better on the box than actual.

    Actual to the tank numbers in mine are .6 lower than what the box says cumulative avg over the life of the truck so far. If I listened to the dummy in the box she thinks I'm almost always over 8 lol
     
    Last edited: Feb 20, 2017
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  10. aussiejosh

    aussiejosh Road Train Member

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    Theres no way you get the same fuel economy at 65 as you would at 80 Increasing your highway cruising speed from 55mph to 75mph can raise fuel consumption by as much as 20%. You can improve your gas mileage 10 - 15% by driving at 55mph rather than 65mph. Its all about your rev's some engines are more economical at 1800 rpm others at 1500 rpm depending on the brand so the lower the revs the better economy your going to get which you can achieve by changing your diff ratio's.
     
  11. Hurst

    Hurst Registered Member

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    65 - 80 mph?

    Most anything above 68 - 69 and mpg drops off exponentially.

    When loaded,.. I personally cruise between 63 - 65 mph,.. I dont care if the speed limit is 75 or 80.

    Hurst
     
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