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Topic: How much DEF should I expect to use (Read 642 times) previous topic - next topic

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How much DEF should I expect to use

I think the subject says it :D

I know this is somewhat engine specific, so could others say what their experience has been in DEF consumption for their engine.  Also curious if anyone with the new X15 engine what you are finding for usage as there was some indication it may be lower than its predecessor.

Re: How much DEF should I expect to use

Reply #1
Cummins will tell you  to expect from 2% to 5% per gallon of Diesel used.  That is quite a range really.

  • 1000 miles at 8mpg and 2% is 2.5 gallons of DEF
  • 1000 miles at 8mpg and 5% is 6.25 gallons of DEF

The smaller engines, such as the ISL 400HP are towards the low end of that range where as the ISX 600 is closer to 4%.  And of course the bigger engines have lower mpg so its a double hit.   Yes this is a generalization, and I'm sure someones Uncle Bumble gets 12MPG on their ISX 600 Cornerstone and uses just 1%, you know its the internet :P

Re: How much DEF should I expect to use

Reply #2
I tend to get around 4-5%  ..

Its difficult to be more accurate than that since I don't have a set level or indicator that I fill the tank to ...  I mean I'll fill up at the truck stop and add 10 gallons or use a couple of 2.5 gallon jugs when needed.   All I know is when it wants more vs a true consumption rate like you can get via the computer for fuel used.  If there is a total flow sensor for DEF, I'd like to know.

Re: How much DEF should I expect to use

Reply #3
I use about 2-2.5% based on various trips and fuel used / DEF added.  Just wish my DEF tank was a bit larger.


Re: How much DEF should I expect to use

Reply #4
I plan on 2.5% as well ... and like @Charlie said, its hard to be exact here since I use those 2.5Gallon boxes to top / fill as needed

Re: How much DEF should I expect to use

Reply #5
My friend has an X15 (SOB) 605hp engine and is getting the same DEF usage as they did in their previous ISX15 600hp, around 4 to 5% usage per gallon of diesel used.

I would say the improved DEF spray pattern and usage etc in the X15 announcement is true but not in the sense that you are going to see it in your DEF tank, as in its not going to reduce usage to  2 or 3%.

Re: How much DEF should I expect to use

Reply #6
I used about 1 gal per 300 mile on a trip. 450h engine, 7.5MPG  70 miles per hour turnpike driving