3.0 Duramax DEF consumption

[UWSkier]

Bumping up this thread to see if the forum has found a solution to the excessive DEF consumption while towing.  I currently have a 2016 5.3L and am about to pull the trigger on a travel trailer that will likely be about 7500 lbs loaded (boondocking with full tanks).  3/4 ton trucks don't fit in my garage since the manufacturers are all designing them with "I'm gonna be a big rig when I grow up" in mind.  Strongly considering the updated 3.0 Diesel in the '22 for my next rig.  Or an F150 Powerboost.

 

I plan on towing annually from Arizona to the Midwest and back and don't want to be stopping to add DEF every 300 miles.

[PinBoss]

On 12/9/2020 at 8:36 AM, BJ Niceguy said:

OK, the gauge is crap. I have 2020 3.0 & have 21K on it (about 1/2 towing). Mine takes forever to work down to 1/2 full on the bars, then almost instantly drops to one bar & throws low alarm. I bought a OBI plug in thing and it reads the def remaining. On mine, when the def tank drops 1st bar, it is really at about 80% remaining, then drops about 10% for each bar till about 1/2 on gauge. On mine when gauge reads 1/2 I am between 45% & 52% (the lower the tank gets, the more the OBI bounces around, assume sloshing in tank). Anyway, when mine hits 42% to 45% it drops to 1 bar & throws low alarm. I can usually BARELY get a 2.5 gallon jug in it & other times if filling at truck stop might get 3 gallons in. I have been in situations where I could not just stop & add, so ran past the 1 low bar & towing it dropped to empty & kinda locks up teh lower part of gauge and starts count down to speed reduction. I have never added more than 3.8 gallons.

 

On Def usage. Mine does not use much when not towing. When towing, how hard I am driving makes huge difference on consumption (as it does with mileage). If towing 5K enclosed trailer at 60 on 2 lane road, the def usage is probably 1/2 of what it is running 75+ on freeway (big difference in mileage too). I have had a 2013 with 6.2, 2016 with 5.3 & now the 2020 with 3.0. For me the 3.0 is hands down the better towing truck.

 

My biggest bitches with truck are the Def gauge & having to push the stop button every time start truck so it does not shut off at lights when not towing

 

 

Found this while Googling about DEF consumption. We have a 2021 Silverado RST with the 3.0 and have been having similar experiences to what seems to be commonly described in this thread.

 

I tow a lot, and while towing, it goes from full to empty within 500-750 miles depending on the load. It's not proportionate to fuel consumption. 

 

Last night I ran out of DEF (according to the gauge) and got to the 500 mile countdown prior to reduced 65 MPH speed limit. I decided to drive 250 miles through that countdown, to ensure I was bone dry for DEF. 

 

Happened to stop at a gas station that had DEF at the pump, and at 3.8 gallons it was overflowing... so either the capacity is not the 5.2 gallons advertised, or there was still over a gallon of DEF left during that countdown. I would find that strange since it literally says that you are OUT of DEF, not just low... but perhaps just addition precaution?

 

I wondered why when I was at 1 bar and out, even trying to fit 1 x 2.5 gallon box of DEF in would result in overfilling. 

 

First diesel for us, so learning as we go. Have a diesel Tahoe on order too, wondering if I should switch to gasoline.

[redwngr]

2 hours ago, PinBoss said:

 

 

 I decided to drive 250 miles through that countdown, to ensure I was bone dry for DEF. 

 

Happened to stop at a gas station that had DEF at the pump, and at 3.8 gallons it was overflowing... so either the capacity is not the 5.2 gallons advertised, or there was still over a gallon of DEF left during that countdown. I would find that strange since it literally says that you are OUT of DEF, not just low... but perhaps just addition precaution?

 

I wondered why when I was at 1 bar and out, even trying to fit 1 x 2.5 gallon box of DEF in would result in overfilling. 

 

First diesel for us, so learning as we go. Have a diesel Tahoe on order too, wondering if I should switch to gasoline.

3.0L duramax supplement says says 5.3 gallon capacity for the LM2 tank.

 

I topped mine up about 700 miles and have done 2 fills since.

5.52 gal and 5.75 gallons.

Second one was after it thought it was empty and was giving the speed limit warnings.

Second one overflowed, first did not. 

 

MPG's were 922 and 1438 over the 13,248 miles for the 2 fills.

 

Not sure it helps you, other than verifying it holds more than 3.8 gal.

[Trubik]

I bought a 2021 3.0 Duramax a year ago, I found this post looking for other drivers with  high DEF consumption issues, to reply to your post, this engine is a real pleasure compared to the 5.3 gas, without a trailer, it average 29 mpg, I did as good as 43 mpg on level highway. It uses about a tank per 5000 miles. While pulling a trailer, it does about 17.5 miles per gallon, and uses a tank of DEF per 900-1000 miles.