DEF - Usage

1006 Views 5 Replies 5 Participants Last post by  Smittys2500
I read a thread on a travel trailer forum that was discussing DEF. The people were saying they are getting about 1500 miles for their DEF tanks, about 2.5 gallons. That seemed to be the norm they were reporting for their 2500 and 3500 trucks.

I just put in my third box of DEF in my 2500 and I have about 12,000 miles. So I figure that is about 5,000 miles for a 2.5 gallon box. I don't put any more than one box in at a time and only put it in when the gauge shows it is almost empty.

I just read a thread on this site, from 2017, where someone said you should get about 5,000 miles on 2.5 gallons of DEF. That same thread said to turn off or change the amount of DEF used. Is that on older system of DEF that can be turned off or amount adjusted?
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I'm averaging around 7300 miles on 5 gallons of DEF on my 17 2500. I'm not aware of any adjustment you can make to the system.
Contiue doing what you're doing and dont stress over it. And no, you cant turn off or vary the amount unless you install a tune that has those features.
The amount used will be determined by a number f factors. Of course, more DEF is used while towing or otherwise placing a load on the truck. Allowing the level in the tank to drop to ~1/4 (or maybe even a bit less) is a good idea, so the freshest mixture DEF can be maintained.
Oh trust me; I'm not losing any sleep over DEF. I was just wondering about it. But I see that I did my math wrong; I'm getting about 1500 miles or so for a gallon of DEF.

I do let the needle get down to the red mark before I put more in the tank. I also don't buy any until I'm ready to put some in, so it's not just sitting in the garage and I only put in one box at a time.

Thanks guys. Guess I'll go back to doing nothing again.
That's better than mine, I have 2200 miles on and it just took a 2.5 gallon and its almost full again.
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