2020 AT4 Duramax - How much Def usage is normal?

fc_glk · October 12, 2020

I have a 2020 at4 with the duramax. My question is, how much def are others' trucks using? Mine seems to be pretty thirsty, much more so than previous diesels I've owned. I'm having to put a box of blue def in about every 600 miles. As soon as I put some in, it says something like '1000 miles of def remaining'. The display shows its full, but then it will drop to 250 remaining within a few hours.

AdamAT4 · October 12, 2020

3.0 or 6.6?

Either way you have a sensor issue or something.

Sent from my SM-T830 using Tapatalk

jnissen · October 12, 2020

How much towing does the truck see and how heavy is your foot? Both have a direct correlation to DEF volume from what I’ve experienced.

btj_z71 · October 12, 2020

34 minutes ago, fc_glk said:

I have a 2020 at4 with the duramax. My question is, how much def are others' trucks using? Mine seems to be pretty thirsty, much more so than previous diesels I've owned. I'm having to put a box of blue def in about every 600 miles. As soon as I put some in, it says something like '1000 miles of def remaining'. The display shows its full, but then it will drop to 250 remaining within a few hours.

I would head up to the dealership ASAP. Something isn't right.

I've got the 3.0L Duramax with 1300 miles on it now, and the DEF is still showing full.

If you are having to fill DEF that often, something is way out of spec.

fc_glk · October 12, 2020

32 minutes ago, jnissen said:

How much towing does the truck see and how heavy is your foot? Both have a direct correlation to DEF volume from what I’ve experienced.

we were towing an RPOD (about 3000lbs) for a few weeks... We noticed it was using a little more def, but now its way more. I am going to take it down to the dealer. We live about an hour from the dealer, so wanted to make sure this isn't normal before I make the trek down there.

Duramax3oh · October 12, 2020

3.0L on Z71 LT

Usage under normal conditions seems to be pretty light. Towing however it will gulp it up. Maybe 1000 miles I'll go through 4 gallons towing a 5800 lb travel trailer. So 1 box of DEF (at 2.5 gal) for 600 miles wouldn't seem to bad IF TOWING. With that said the DEF Gauge is terrible inaccurate during usage and when refilling.

redwngr · October 12, 2020

Should be somewhere 2 gal def per 100 gal fuel.

newdude · October 12, 2020

5 hours ago, fc_glk said:

I have a 2020 at4 with the duramax. My question is, how much def are others' trucks using? Mine seems to be pretty thirsty, much more so than previous diesels I've owned. I'm having to put a box of blue def in about every 600 miles. As soon as I put some in, it says something like '1000 miles of def remaining'. The display shows its full, but then it will drop to 250 remaining within a few hours.

You've got a problem then. Is the check engine light on?

Edited October 12, 2020 by newdude

thegrizz · October 14, 2020

Agreed. Take it to the stealership.

I have hauled around town several weekends and still have not added any since I bought it. Sitting at 4,100 miles.

wo_allvol · October 19, 2020

I'm curious as well.. I never tow anything and I'm at 1400 miles and my gauge hasn't moved.

Wintersun · October 20, 2020

DEF consumption should be 1 to 1.5 percent of the diesel burned. If the truck burns 100 gallons of diesel then it should not use more than 1.5 gallons of DEF. The computer relies on NOx sensors to determine how much DEF to add to the exhaust stream from the engine. If the sensor is failing or the programming is not done correctly then the DEF consumption can increase dramatically. I also found with my Duramax that the error codes were always incorrect which was the result of flawed controller programming by the kids at General Motors.

Out of 6 Chevy dealers I was only able to find one dealer with one mechanic who actually knew how to diagnose problems with the diesel DEF systems. My truck was manufactured in 2011 and clearly GM has not improved their sensors and their programming since that time. I had the truck go into limp mode 4 times while more than 1000 miles from my house. I stopped using the truck for travel as it was not reliable.

AdamAT4 · October 20, 2020

DEF consumption should be 1 to 1.5 percent of the diesel burned. If the truck burns 100 gallons of diesel then it should not use more than 1.5 gallons of DEF. The computer relies on NOx sensors to determine how much DEF to add to the exhaust stream from the engine. If the sensor is failing or the programming is not done correctly then the DEF consumption can increase dramatically. I also found with my Duramax that the error codes were always incorrect which was the result of flawed controller programming by the kids at General Motors.

Out of 6 Chevy dealers I was only able to find one dealer with one mechanic who actually knew how to diagnose problems with the diesel DEF systems. My truck was manufactured in 2011 and clearly GM has not improved their sensors and their programming since that time. I had the truck go into limp mode 4 times while more than 1000 miles from my house. I stopped using the truck for travel as it was not reliable.

I'm convinced there's still no diesel exhaust treatment system that actually works, and only gets worse in cold or heavy duty applications. Thats one reason ill never own a diesel that can't be deleted. When I bought my Ram I thought I'd leave it stock for 2 to 3 years and after a few months I had 2 codes so got rid of it then went 5 years with no issues.

My old man has a 16 LML and after a few years he started have so many issues he finally broke down and got it deleted and remembered how much he was missing (his last duramax was tuned from day 1)

Sent from my SM-N975W using Tapatalk