Have a 2023 Duramax and with 2,700 miles def range popped up 159 miles left. I haven’t towed anything at all and just normal highway driving. When I picked it up the def gauge read full on the bars. Any ideas? Cause for concern?
High Def Usage
- Thread starter Bpamgat4
- Start date
Cocoabean
Well-known member
A lot of it is dependent on usage. If the truck was used for test drives and short trips, it might use more as the truck wont burn off soot as well. These trucks like long drives and pulling weight. I get about 3k-4k on a tank of DEF. You will likely see the same as you add miles on the truck.
slythetove
Active member
DEF is not used to burn off soot that’s called a regen and it cleans the DPF with high heat by dumping extra fuel.
DEF is used constantly in small amounts.
If you had a full DEF tank and have done no towing ( which does increase DEF usage ) I would say you have abnormal usage if you only got 2300 miles for the whole tank.
My DEF tank went almost 7500 miles and I towed only a couple of times maybe 20 miles total.
Fill the tank to be sure it’s full and take note of the mileage and if it’s dropping fast like that still I’d say have it checked out. I’ve read other threads from folks with abnormal usage that needed something replaced.
Best of luck
DEF is used constantly in small amounts.
If you had a full DEF tank and have done no towing ( which does increase DEF usage ) I would say you have abnormal usage if you only got 2300 miles for the whole tank.
My DEF tank went almost 7500 miles and I towed only a couple of times maybe 20 miles total.
Fill the tank to be sure it’s full and take note of the mileage and if it’s dropping fast like that still I’d say have it checked out. I’ve read other threads from folks with abnormal usage that needed something replaced.
Best of luck
Cocoabean
Well-known member
Wow I was off. I had regen in my head and thought DEF was used more during this cycle. Apologies to the OP for any confusion.
I only got about 4k on my first tank of DEF, so I guess I need to keep and eye on it this tank.
slythetove
Active member
Did you do any significant towing? If so 4k could be totally in line. DEF usage correlates to fuel usage so more towing means lower mpg for both fuel and DEF. I think this is the simplest way to think of it. DEF is used in direct relation to fuel used. Undoubtedly there is a formula that tells exactly how much but I have no clue what the formula is.
Cocoabean
Well-known member
No, I haven't towed anything yet. I am running 35's, so my mpg averages 19. Highway I get 21-23, but city is about 15-17.
slythetove
Active member
Given that mpg it may be totally normal at 4k miles. I'm generally 25+ mpg
I came from a 2016 Ram EcoDiesel 3.0 and it didn’t drink as much DEF as my 2023 3.0 duramax. I have 4100 miles and have added 5 gallons of DEF, on my EcoDiesel I added about 5 gals every 10,000 miles, so it’s useing more than double
EPA's NOX limits has decreased since '16, so ya, we will all be using more def. And it's not going to get better, till we abolish the EPA.
Won't be long and the def tank will be bigger than the fuel tank.
Lawdog800
Member
SO my 2023 1500 AT4 with the LZ0 got 656 mpg of DEF the last tank and showed an average of 516.4 in 8887 niles tracked on Fuelly app. yesterday It was drinking DEF like going out of style pulling a new 7 ft wide 18 ft+6 ft v nose sled trailer 7 ft height inside trailer. It used 2.5 gallons of DEF in 400 miles....trailer empty 2500 lbs. Got a warning of LOW DEF - Speed limited soon - bought a box at Wallyworld. added the 2.5 gals then got some and light came back on just before got home..65-77 mph speeds. maybe needs a dealer trip....
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slythetove
Active member
If I'm following your outline correctly you say "656 mpg of DEF" which to me translates to 656 x 5 = 3280 miles on a 5 gallon tank. The rest of your math gets worse from there. That's definitely excessive in my opinion, unless all your mileage was towing 5000lbs+
I went about 7500 miles on my first 5 gallons of DEF. I towed a few times maybe total of about 30 miles with 4000lbs and 20 miles with 9000lbs. so mostly non-towing miles.
Hope that helps provide a frame of reference.
Andystoy AT4
Active member
Since DEF usage is based on the amount of fuel you are burning (IDK the formula) how much fuel did you use during the same tow. That may shed some light on how hard the engine was working?
Lawdog800
Member
Def said Low -speed limited soon. Added 2.5 gallons drove 400 miles freeway driving. Empty trailer. Fuel mileage was 13.7 mpg hand calculated. Def back in red Low speed limited warning on again. Trailer weighs 2500 lbs. just an empty box.
That sounds about the same DEF usage my 2020 AT4 3.0 used for me when pulling a trailer. But even when not pulling a trailer, I never got the DEF mileage most in this thread are getting. IDK if something was always not quite right with my DEF emissions system or what. I had to trade the truck in early January as the continual "service emissions system" warning came on and all "fixes" the dealership tried, failed. Put me into severe limp mode, stranding me out of state for a month. Dealership never could get it fixed. So I traded it for my 2023 AT4X (which itself is right now in the dealership shop as the electronics were bricked on it this morning).
