DEF usage on 2020 HD models

Wbrisett · October 1, 2020

I just returned from a 2,000 mile trip. During this trip I put in 5 gallons of DEF (and my GMC is telling me it's ½ full now and I have 1000 miles of DEF range left)... Really??? My 2015 Chevy 2500 HD didn't nearly drink this much DEF. I know emission standards have tightened up a bit, but this seems a bit extreme. Is 7 ½ gallons for 2,000 miles normal? (I'm guessing another 2 ½ gallons based on how much I had to put in last time). The only silver lining is I have a fleet account and can use the trucking lanes for filling up, which have DEF at the pump, but this usage seems way too high. What are others seeing with 2020 models?

Thankful · October 1, 2020

I think 7 and 1/2 gallons is too much for a 2,000 mile trip. I traveled to New York last month, almost 2,000 miles there and back, and only used about 4 gallons. What really blows my mind is how a mixture of urine and water costs more than diesel fuel.

kylant · October 1, 2020

I know there is an update for excessive DEF usage. probably want to head to the dealer to have it done

redwngr · October 1, 2020

The DEF gauge is NOT a simple variable gauge like a fuel gauge.

It also blends in an estimate of the remaining range (like the range estimate for fuel in the dic).

The only way to know miles per def gallon is to fill it, drive it for a few thousand and refill it. Just like a hand-calc for fuel mileage.

https://gm-techlink.com/?p=13143

Diesel Exhaust Fluid Consumption

May 21, 2020

The diesel engines (RPOs LWN, LM2, L5P, L5D) available on 2020 Colorado, Express, Silverado 1500, Silverado 2500HD/3500HD, Silverado 4500HD/5500HD/6500HD, Canyon, Savana, Sierra 1500, and Sierra 2500HD/3500HD models use Diesel Exhaust Fluid (DEF) (Fig. 1) in order to reduce the exhaust Oxides of Nitrogen (NOx) levels within the Selective Catalyst Reduction stage of the exhaust aftertreatment system. A series of driver prompts and warnings are initiated when the DEF level falls below a calibrated value.

Fig. 1

Segmented DEF Level Gauge

The current 2020 Silverado 1500 and Sierra 1500 models have a DEF level gauge on the instrument cluster that provides drivers with a representation of how much DEF is in the DEF tank up. (Fig. 2) The DEF level gauge does not operate like a typical float-style gauge that is used in a fuel tank. The Engine Control Module (ECM) monitors the DEF level and consumption rate in order to calculate an estimated range. DEF levels are detected by the DEF level sensor.

Fig. 2

There may be some fluctuation in the amount of DEF represented on the DEF level gauge. After filling the DEF tank, it may take a few key cycles to register the correct amount in the DEF tank. With the new segmented DEF level gauge, it is possible that after adding 5 gallons (18.9 L) of DEF that the gauge reads as a full tank after the fill event. However, if the actual level of DEF is just entering the last segment on the gauge, the gauge is likely to drop by one segment shortly after driving after the fill event. As a result, a driver could have an initial impression that the vehicle consumes an excessive amount of DEF.

Emissions Requirements

Every year, GM produces diesel engines that continue to meet aggressive federal requirements to reduce Nitrogen Oxides (NOx) in the vehicle exhaust. As DEF is required to reduce the NOx in the exhaust, DEF consumption will increase as NOx reduction requirements increase. Customer trading in an older model year diesel vehicle for a newer model year vehicle will likely see an increase in DEF usage. DEF consumption increases as the newer vehicles meet the more stringent emission requirements for that model year.
The amount of DEF consumed also is a function of how hard the engine is working, or engine load. Due to engine use, it is more representative to compare DEF consumption to the amount of fuel consumed – also a function of engine load – instead of miles traveled. In addition to engine load, other factors that affect the DEF usage rate are the humidity, temperature, and altitude where the vehicle is operating.

Under certain conditions, the ECM will increase or decrease the amount of DEF used based on learning or adaptive algorithms. In the event of a malfunction and Check Engine light, the ECM may double or even eliminate the amount of DEF that is being used. An improper amount of DEF use will continue until the vehicle is repaired and the learned value in the ECM is reset.

shadow gray 2020 hd · October 1, 2020

From the way I read the above, there is not a typical tank float level sensor that might get stuck? I have not added any def to my tank in over 500 miles. The display when I added went to one bar less than full, but I know it was full at that time. A day or so later with maybe 100 miles of driving, the display showed full and is still showing full now. Is this normal?

Londart2020 · October 2, 2020

7 hours ago, shadow gray 2020 hd said:

From the way I read the above, there is not a typical tank float level sensor that might get stuck? I have not added any def to my tank in over 500 miles. The display when I added went to one bar less than full, but I know it was full at that time. A day or so later with maybe 100 miles of driving, the display showed full and is still showing full now. Is this normal?

I just asked this same question as I am experiencing the same thing...down a square, now full again, even after towing my TR 200+ miles...

Wbrisett · October 2, 2020

I too see even full that the DEF gauge shows one bar down. I might have a chat with my local dealer and see what they think. Just seems to me that 7+ gallons for 2,000-ish miles (closer to 2400) is too much. I do wonder if they need to reset something after reading that bulletin.

cNate · October 2, 2020

There’s a service bulletin for this. I had the same issues and haven’t had them since. My sensor reads accurately now. I am burning a lot of DEF fluid compared to previous generation trucks but it’s definitely improved after the service bulletin: sensor is spot on now and mileage has increased.

I was getting 300-400 miles per gallon on DEF the first 11k miles and now I’m seeing closer to 700-800 miles per gallon over the last 4K miles after service. Same driving conditions.

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migrabill · October 2, 2020

When I fill mine - it shows half full.

mdbourque · October 2, 2020

I have the 2020 Silverado 2500 HD and just got back from a 3700 mile trip towing a ~7000lb travel trailer. I had to fill my 4.5 gallon DEF tank three times! It eats DEF like crazy. Mine starts giving me warnings that my DEF range is 975 miles about 150-200 miles after I fill it. Also, about 20 miles from home the DEF gauge went from 3/8 to 0 in one step and told me "DEF low, speed limited soon". The DEF sensor is seriously goofed up and the 2020 is using a *lot* of DEF. They did the DEF related software update when I got back but I have not been towing to see if it still uses an exorbitant amount of DEF.

Wbrisett · October 3, 2020

Got an appointment for them to look into it today. I'll post how that goes.

Wbrisett · October 6, 2020

On 10/2/2020 at 10:03 AM, cNate said:

There’s a service bulletin for this.

Any idea what that bulletin is? My dealer says he can't find anything and service tech looking at the truck can't find anything, so he's saying 7 ½ gallons for a 2200 trip is about right. ... I find that hard to believe. Unless you're now carrying boxes of the stuff around all the time or can find stations with DEF at the pump, they are really handicapping folks. I think I'm using way too much.

cNate · October 8, 2020

Any idea what that bulletin is? My dealer says he can't find anything and service tech looking at the truck can't find anything, so he's saying 7 ½ gallons for a 2200 trip is about right. [emoji44] ... I find that hard to believe. Unless you're now carrying boxes of the stuff around all the time or can find stations with DEF at the pump, they are really handicapping folks. I think I'm using way too much.

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cNate · October 8, 2020

My dealership had no idea either. I asked them to search for it based on a post I read on another forum and they found. See number in photo I posted.

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Wbrisett · October 8, 2020

4 hours ago, cNate said:

My dealership had no idea either. I asked them to search for it based on a post I read on another forum and they found. See number in photo I posted.

I read that bulletin, I don't think that's it... but it's worth a shot.

https://static.nhtsa.gov/odi/tsbs/2020/MC-10176821-9999.pdf