2016 DEF gauge

[CSeugling]

Hi all, Just took a trip NJ to Florida with my 2016 3500, 6.7 aisin, rambox pick up, towing empty 12ft enclosed trailer. Before leaving I topped off the def tank 2.5 gallons, gauge read 100%. Went 1100 miles to destination and def gauge read just under 1/2, 50%. I bought a box 2.5 gal and put it in before returning home. Now on the ride home the trailer was loaded and was about 3500 lbs in total weight. Again 1100 miles but this time the def gauge never moved off 100 %. Drove the truck a few times locally and still at 100%. Took it to the dealer and they tell me the gauge is part of the pump and it all has to be replaced. I have the max care warranty and they said it will cover this except $100.00 deductible. The parts are on national back order as they put it, and they would be lucky to see the pump before May 1,2021. Driving the truck for the past 2 weeks and it seems that the gauge is now coming off 100% just slightly, but it has come down a little. So my question is, is there any way I could not be using all that much DEF?? By my calculations 1100 miles down, about 80 gals of diesel and the same coming home, so about 3.5 gals of def??

 

[Ltngdrvr]

There is absolutely nothing wrong with the gauge, it is working just like all of them do.
The gauge is not linear, and there is about 1.5 gallons ABOVE full.
The first time you added 2.5 gallons, you didn't get it anywhere near to actually full, then you drove it down to where the gauge showed about 1/2, then added another 2.5 gallons, and that probably filled it a little more than the first 2.5 gallons did.

DEF usage is generally about 2-3 percent of fuel usage, so the better fuel economy you get the less DEF is used.

If you really want to fill the DEF tank, go to the truck stop and fill it at the pump like the 18 wheelers do.
Then it will go a VERY long time before the gauge level starts to drop.

 

[CSeugling]

Thanks that's what I was thinking also. I'll keep using the truck and monitor the gauge.

 

[lpennock]

As CSeugling said. It isn't linear.

On mine when you fill DEF to the top, it will go 1-2K miles before moving off Full depending on load. Then it will slowly drop until it give you the DEF low warning. As long as it went up when you put some in it is fine.

 

[AH64ID]

As others have stated everything seems normal.

I get ~1000mpg DEF empty and ~500 mpg DEF towing, with a lifetime average of 872 MPG at 1.6% of my diesel rate.

I try to only fill up at the pump as it's the only really good way to track usage.

 

[Ltngdrvr]

Trying to track actual DEF usage, DEF MPG, is just a short trip to exasperation and stress.
I gave up a long time ago, sometimes the DEF MPG is high, sometimes it drinks the stuff like it was free.
I've gotten to the point where if I get a full trip to Indiana and back to Texas on a tankful, then I'm good.

 

[AH64ID]

Trying to track actual DEF usage, DEF MPG, is just a short trip to exasperation and stress.
I gave up a long time ago, sometimes the DEF MPG is high, sometimes it drinks the stuff like it was free.
I've gotten to the point where if I get a full trip to Indiana and back to Texas on a tankful, then I'm good.

It's actually quite easy to calculate, and easy to correlate. More power = more DEF use. EGR is reduced as engine load goes up, so that explains the increase in DEF usage.

 

[Ltngdrvr]

It's actually quite easy to calculate, and easy to correlate. More power = more DEF use. EGR is reduced as engine load goes up, so that explains the increase in DEF usage.

I know the correlations of DEF usage, often my truck doesn't know them.
If the DEF you get is weak, the ecm calls for more to be injected, trying to get the NOx numbers inline, completely throws off the normal usage curve.

 

[smittyd174]

Hi all, Just took a trip NJ to Florida with my 2016 3500, 6.7 aisin, rambox pick up, towing empty 12ft enclosed trailer. Before leaving I topped off the def tank 2.5 gallons, gauge read 100%. Went 1100 miles to destination and def gauge read just under 1/2, 50%. I bought a box 2.5 gal and put it in before returning home. Now on the ride home the trailer was loaded and was about 3500 lbs in total weight. Again 1100 miles but this time the def gauge never moved off 100 %. Drove the truck a few times locally and still at 100%. Took it to the dealer and they tell me the gauge is part of the pump and it all has to be replaced. I have the max care warranty and they said it will cover this except $100.00 deductible. The parts are on national back order as they put it, and they would be lucky to see the pump before May 1,2021. Driving the truck for the past 2 weeks and it seems that the gauge is now coming off 100% just slightly, but it has come down a little. So my question is, is there any way I could not be using all that much DEF?? By my calculations 1100 miles down, about 80 gals of diesel and the same coming home, so about 3.5 gals of def??

Hi all, Just took a trip NJ to Florida with my 2016 3500, 6.7 aisin, rambox pick up, towing empty 12ft enclosed trailer. Before leaving I topped off the def tank 2.5 gallons, gauge read 100%. Went 1100 miles to destination and def gauge read just under 1/2, 50%. I bought a box 2.5 gal and put it in before returning home. Now on the ride home the trailer was loaded and was about 3500 lbs in total weight. Again 1100 miles but this time the def gauge never moved off 100 %. Drove the truck a few times locally and still at 100%. Took it to the dealer and they tell me the gauge is part of the pump and it all has to be replaced. I have the max care warranty and they said it will cover this except $100.00 deductible. The parts are on national back order as they put it, and they would be lucky to see the pump before May 1,2021. Driving the truck for the past 2 weeks and it seems that the gauge is now coming off 100% just slightly, but it has come down a little. So my question is, is there any way I could not be using all that much DEF?? By my calculations 1100 miles down, about 80 gals of diesel and the same coming home, so about 3.5 gals of def??

It soounds normal to me . Not towing I can almost go oil change to oil change if its topped off. (12000 kms or about 7500 miles). Towing 14000 lbs around 3500 miles give or take. I thought it was broke when I got my 16 because the needle was stuck on full. Didn't move for 1000 miles. Don't worry about ,fill it when it gets low. I let mine get to about 1/4 then add a jug. Be careful don't overfil in cold climates cause it will freeze , expand and crack the tank.
.

 

[AH64ID]

I know the correlations of DEF usage, often my truck doesn't know them.
If the DEF you get is weak, the ecm calls for more to be injected, trying to get the NOx numbers inline, completely throws off the normal usage curve.

Whats often? Do you regularly get bad DEF?

Yes some weak DEF will burn faster but that shouldn’t be any more common than a tank of bad diesel.

 

[Ltngdrvr]

Whats often? Do you regularly get bad DEF?

Yes some weak DEF will burn faster but that shouldn’t be any more common than a tank of bad diesel.

It's not bad DEF, just less potent, for one reason or another, and that would be a reason that the truck would use(not burn) more DEF.
NOx sensor tells the ecm that the NOx levels are too high and more DEF is injected to help compensate, this happens when the DEF potency is lower, same as when engine load is higher, combine both and the DEF pump can run out of capacity too.
Anyway, point was that there are many factors that can skew expectations of how much DEF should be used.
And, none of this has anything to do with the OP's original question, which was answered already.

 

[AH64ID]

It's not bad DEF, just less potent, for one reason or another, and that would be a reason that the truck would use(not burn) more DEF.
NOx sensor tells the ecm that the NOx levels are too high and more DEF is injected to help compensate, this happens when the DEF potency is lower, same as when engine load is higher, combine both and the DEF pump can run out of capacity too.
Anyway, point was that there are many factors that can skew expectations of how much DEF should be used.
And, none of this has anything to do with the OP's original question, which was answered already.

How often are you getting weak DEF? You said your truck often doesn’t know the correlation. So what’s often?

 

[Cummins12V98]

All I have ever heard is DEF is DEF with ZERO difference. Now we have "weak" DEF???

 

[lpennock]

DEF spec is UREA 32.5 +- 0.7 % so weak would be 31.8% and strong would be 33.2% I guess.

 

[AH64ID]

DEF spec is UREA 32.5 +- 0.7 % so weak would be 31.8% and strong would be 33.2% I guess.

Even then you can get lower % and not get a CEL. The early DEF trucks are more tolerant, in terms of a CEL, than the more recent DEF trucks. I don’t recall when the programming got more stringent.

 

[sag2]

Take a look at The Rest of the Story, issues 102 and 109 for more info in DEF concentration. DEF will naturally go more concentrated as water evaporates. The only way it can get diluted is if someone adds water (see issue 109) or it comes that way, which is highly unlikely. Changing it by a couple percent is not going to result in a significant increase in use.