[hotairgypsy]

I have been troubleshooting if I have a DEF issue with my new truck. I picked up my new truck the beginning of December with 44 miles on it..as of today I have 3700 miles on it and I have already put in 4 2.5 gallon DEF containers...This does not include what ever the truck came with...If i remember it had half tank...I have had it into the dealership 2 times for this. First time they did a software update and sent me on my way. A couple of days ago they called GM and they were asked to preform a DEF consumption test on the truck. So they filled up the truck with DEF and sent me on my way telling me to return when I am at half DEF tank. I asked the service adviser if they had an opinion at this point and I was told it just uses more due to more horsepower. I call BS on this. My 2015 used 5 gallons every 5000 miles. This truck has used over 12 gallons in under 3700 miles.

So I have a simple question for you all...I just want to know how many miles are you getting before adding DEF...Thanks gang

 

[Collins]

2019 with 10kmiles. I'm averaging around 750 miles/gal def

 

[hotairgypsy]

i assume none of ya use and DEF it seems

 

[ipogsd]

I got it filled at my first, free, service. Took 4.5 gallons after 2400 miles. Will be the only time it gets refilled however 🙂

 

[redwngr]

I have been troubleshooting if I have a DEF issue with my new truck. I picked up my new truck the beginning of December with 44 miles on it..as of today I have 3700 miles on it and I have already put in 4 2.5 gallon DEF containers...This does not include what ever the truck came with...If i remember it had half tank...I have had it into the dealership 2 times for this. First time they did a software update and sent me on my way. A couple of days ago they called GM and they were asked to preform a DEF consumption test on the truck. So they filled up the truck with DEF and sent me on my way telling me to return when I am at half DEF tank. I asked the service adviser if they had an opinion at this point and I was told it just uses more due to more horsepower. I call BS on this. My 2015 used 5 gallons every 5000 miles. This truck has used over 12 gallons in under 3700 miles.

So I have a simple question for you all...I just want to know how many miles are you getting before adding DEF...Thanks gang

The only accurate way to now how much it is using is to fill it, drive it several 1000 miles (and more is better, since they don't use a lot) and refill it. Because it uses a small amount, measurement error can be large.
It's difficult to know if it is filled to the same point, especially with jugs.

Starting with an unknown amount in tank since level indicator is a guess, and lots have reported it as incorrect) and dumping in jugs along the way isn't giving you the info you want.
The level indicator isn't accurate enough for this test.

If the factory only put's in a couple gallons, then it could have taken the first 2 jugs would have filled it.
If two jugs were just added, and it's now back to full again, then that's 2 jugs for 3700 miles.


I'd recommend getting it full and starting the test over.



DEF usage is a % of fuel used. More power (fuel) uses more def. Means that if towing uses twice as much fuel as daily driver usage, then the towing def consumption will also be twice as much as the daily driver def consumption.

Higher def consumption is only going to happen when the higher power levels are used. The NOx sensors are there to give the computer the info it needs to adjust the def injection level to what is required for the fuel being burned.


If the fuel usage is close to the same as your LML, def usage should also be close to the same.

 

[elkhornsun]

It should be less than 2% of the fuel consumed and you can check the reading on the display as to gallons burned. A faulty NOX sensor can cause the computer to add more and more DEF to the exhaust stream and greatly increase the amount consumed per gallon of fuel burned.

 

[hotairgypsy]

i have not seen a gallons burned screen...how do i get to it?

 

[redwngr]

i have not seen a gallons burned screen...how do i get to it?

Gonna have to write it down, or use one of the mpg screens to calculate it.

They haven't had a gallons/litres used screen for a long time.


I use 'trip B' as a life of vehicle economy screen and 'trip A' to compare with hand calc each tank. If you go to the options section where you can select which pages to display the Trip B can be turned off so someone else running the truck won't reset the wrong one if they need to fill it.
(Yupp -- I'm one of those guys; still write it down in a little book too)

 

[BrokenBackJack]

Our 16 isn't bad for DEF usage unless we are pulling. Then it takes much more and this makes sense being using more fuel when pulling.

 

[DMaxRocks]

I've had my '20 for almost 3 weeks and getting close to 2k miles. I didn't pay attention to the DEF gauge when i picked up the truck, but have recently started checking it and have over half a tank per the bar graph on the DIC.

 

[sdelam]

My first tank went really fast, less than 3k if I remember correct. Half of that was towing but still seemed reallly quick. It has gotten better now but I havnt been tracking milage really. Dealer tops it off everytime I took it in so its hard to know for sure how much I've used. The bigger issue for me was that the gauge was all over the place. Sometimes it was full, sometimes it was empty, just no cositancy. I run a Banks iDash and it will show DEF tank level as a percentage. I have found that I get the 1k warning in the truck at about 40% per the iDash, which is only 1 bar on the trucks gauge.

 

[MIkey52]

The reason it went quick on the first tank, is because the dealers don't fill them up before delivery.

 

[sdelam]

Thats what I was thinkin also, it was a 20 though so it has a "gauge" that showed full. have since learned it is not very accurate so they probably just put enough in to make it read full.

 

[Doverarjim]

My 2011 truck averaged 1113 miles to the gallon of DEF, the 2019 truck is averaging 789 miles to the gallon of DEF doing the same type of driving.

 

[braz28]

MY 2020 is a pig for DEF consumption, when pulling 13 000lbs at highway speeds it will burn 2.5 gallon of DEF per 2 tanks.

 

[Area Man]

The reason it went quick on the first tank, is because the dealers don't fill them up before delivery.

You're buying from the wrong dealers, then.

No matter what I've bought, or when I've bought it, everything has been topped off when I buy from my regular dealership. And that's why I keep going back.

 

[sambor]

Quit guessing-- fill the tank till it overflows then you KNOW you have a full tank. Drive it like you normally do for a couple of thousand miles then fill it to the brim again. Now you can figure how much you use.
By the way, my 4500HD gets about 7-900 miles to gallon of def.
Like everbody has said-- it totally depends how you drive

 

[MIkey52]

Quit guessing-- fill the tank till it overflows then you KNOW you have a full tank. Drive it like you normally do for a couple of thousand miles then fill it to the brim again. Now you can figure how much you use.
By the way, my 4500HD gets about 7-900 miles to gallon of def.
Like everbody has said-- it totally depends how you drive

Which is the more fuel you burn per mile the more def you will use per mile. It takes so much def to neutralize the NO2.

 

[hogdooz]

My 2019 GMC 2500HD Denali Diesel has been using excessive amounts of DEF since I got it. It's been to multiple dealers multiple times. I've finally been home long enough to take it to my purchasing dealer. They said they found the DEF injector nozzle injecting more than specified. I just did a test on a trip to Texas, tank was full to the top, highway driving (21 mpg), light load not towing, I got just over 3700 miles before I got the Action Required notification (which is my first notification). I drove another 100 miles until I got a 60 miles left warning so I stopped and added 7 Gallons of DEF. I just got the truck back from the dealer, they said, according to GM instructions, they did the tests GM required and GM said it's OK to release back to me. The dealer thinks it's using way too much but they can't get GM to approve any other work including Nox sensor replace, which they think would help the problem. Before the DEF injector was replaced, towing I got 1500 miles on a 7 gallon tank and 2500 miles not towing. So the injector replacement helped a little but still not close to where it should be. My 2016 Silverado Duramax got 5000 miles on the 5 gallon tank towing. If anyone has any ideas on how to get the dealer to replace the sensors, or any other ideas on how to get GM to respond, please let me know. Thanks.

 

[Chico and the Man]

My 2018 runs very close to 1900 miles per 5 gallon fill and that is pulling 10 to 12 thousand pound trailers half of the time. I have done the math on gallons of Def per gallons of fuel and i am at 3.75 percent of Def usage which i think is excessive but i have not gone to the dealer about this. i have seen posts that say they run around 2% so i wonder what a dealer will say is normal.