DEF usage

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Davehrose1, Jun 22, 2024.

  1. Davehrose1

    Davehrose1 Bobtail Member

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    Hey everyone

    how much DEF is everyone using. It seems like I need a tank every week averaging 400 miles a day mainly highway. Is that normal usage and is there anything I can do to lower it
     
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  3. AModelCat

    AModelCat Road Train Member

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    Normal for what?

    How large is the tank? Most mfg's have different tank size options. Give us some hard numbers in terms of DEF MPG so we have something to work with.
     
  4. Davehrose1

    Davehrose1 Bobtail Member

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    It’s a 14 to 15 gallon tank I think.
    1600 miles for 13.5 gallon def mainly hwy driving
     
  5. AModelCat

    AModelCat Road Train Member

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    DEF usage

    Sounds like you're right in the range at 118 MPG on DEF. Newer engines are using more DEF because of NOx reduction targets on newer engines.
     
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  6. Davehrose1

    Davehrose1 Bobtail Member

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    Does DEF usage get measured by mpg as opposed to type of driving like hey vs local?
     
  7. Magoo1968

    Magoo1968 Road Train Member

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    Def usage is tied to nox which goes up when cylinder pressures rise aka bucking wind , hard on the fuel, heavy loads at higher speeds. Whenever higher horsepower is needed it uses more def.
     
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  8. North Pole Nightmare

    North Pole Nightmare Heavy Load Member

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    4-5 gallons,500 miles,2023 X15,565 hp.
    165,000 lbs 65 mph.
     
  9. tscottme

    tscottme Road Train Member

    My habbit was to fill-up DEF about every third fuel fill-up. Every fuel purchase for me was a fill-up. So I'd estimate 1000-1500 miles between DEF top-off. I usually had 1/4 or more DEF remaining when I added to it.
     
  10. OlegMel

    OlegMel Light Load Member

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    Mine is 1 deff fill up to 3 diesel fill ups…. I used to have high def usage some time ago.. had def fluid filter replaced, found a crack by the doser annd had it welded. also replaced the doser injector. I think your usage is normal.
     
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