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DEF Usage…..

mark1968
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mark1968 Enthusiast

mark1968

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So we were fortunate to buy one of the new 3.0 diesels in early 2020. We enjoyed that GMC denali for the last few years but with all our long distance driving between our kids/home, it was reaching 100k miles and I read great things about the updated 3.0 (LZ0) and decided to trade in our 2020 and get a 2024 ZR2 Bison with the 3.0.  

For the last week we have been breaking the new truck in and driving across country.  We were very used to the DEF usage on our 2020 and with a 1000mile trip we’d normally (not towing) see about 2 blips down on the DEF guage.  However with the new truck, we are seeing significantly more DEF usage on basically the same trip (more than half way down) so we are kind of surprised.   I know Ive read of other owners who had the original 3.0 diesels engine and traded up to the new LZ0 one, so what has been your experience?  Love to hear feedback?? Thanks!

CamGTP Senior Enthusiast

CamGTP

Posted
Posted

I don't have first hand experience with the diesel but some food for thought is that the emissions standards between 2020 and 2024 are possibly different and or that GM is a little ahead of the curve for changing standards and they want to meet those new requirements. So that way they stay compliant in the states that really crack down on testing. Also the ZR2 bison will make the truck work harder to do the same thing compared to your old truck. A lifted truck with heavy duty tires is causing more DEF usage.

newdude Senior Enthusiast

newdude

Posted
Posted
2 hours ago, mark1968 said:

So we were fortunate to buy one of the new 3.0 diesels in early 2020. We enjoyed that GMC denali for the last few years but with all our long distance driving between our kids/home, it was reaching 100k miles and I read great things about the updated 3.0 (LZ0) and decided to trade in our 2020 and get a 2024 ZR2 Bison with the 3.0.  

For the last week we have been breaking the new truck in and driving across country.  We were very used to the DEF usage on our 2020 and with a 1000mile trip we’d normally (not towing) see about 2 blips down on the DEF guage.  However with the new truck, we are seeing significantly more DEF usage on basically the same trip (more than half way down) so we are kind of surprised.   I know Ive read of other owners who had the original 3.0 diesels engine and traded up to the new LZ0 one, so what has been your experience?  Love to hear feedback?? Thanks!

 

 

GM has an updated info bulletin about DEF usage on 2020-up trucks. 

 

READ HERE  - Unable to Fill the DEF Tank – TechLink

 

TLDR, don't add DEF until you see the countdown warning for "65MPH soon".  The algorithms are always changing the amount of DEF used based on fuel consumption.  

 

AND HERE - Diesel Exhaust Fluid Consumption – TechLink

 

The DEF dosing strategy will increase DEF injection when working the engine hard, especially during towing or high payload situations.  Also see ever changing emissions requirements.  Also, you now have a ZR2 Bison which is much less aerodynamic and fuel efficient than your 2020 Denali was which means increased DEF usage even when empty because lower MPG.  

 

 

redwngr Senior Enthusiast

redwngr

Posted
Posted (edited)

I had a '21 LM2 and now a'23 LZO

 

I don't put much faith in estimating def usage per segment.

 

All def added as been from a metered pump, and when def is added the tank gets filled so I can do def mileage calcs the same way as fuel mpg. 

 

The truck is using def at the expected rate of 2% of fuel (2 gal def per 100 gal fuel). The older truck, and the 6.6's I ran before were all very close to the 2% of fuel usage rate.

 

Lifetime average currently 1380 miles per gallon. (first 24,734 miles)

image.png.c7ae13bbe7c4248f7559dde1683edb66.png

 

 

My question would be how does the fuel economy / fuel used during the trip compare with the previous truck? 

It it used more fuel -- speed, headwind, ac running hard due to highe temps, etc -- then it should use more def.  

 

 

 

Edited by redwngr
mark1968 Enthusiast

mark1968

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Posted

I really appreciate the comments!   I was also thinking that the ZR2 Bison is heavier than the Denali and less aerodynamic so that could be part the difference.. On our normal round trip run of about 2k miles, on the old Denali we would get about 24 mpg.. On this trip we just finished we got about 21 mpg.. I expected lower mpg due to the lift but had not considered a big DEF difference.. I guess ill keep monitoring and see if it is around the 2% of fuel usage.  As a side note, we do love the truck.. it is a beast and more suited to the remote area we live in now..

 

What’s interesting is our son also just bought a Trail Boss with the new 3.0 and I drove it back to East Coast for him. Even with the lift i didnt see the level of DEF usage we saw on this trip with the ZR2.  So there must be a factor of weight and we did have some headwinds coming West yesterday.. Anyway, thanks again for everyone’s thoughts!

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