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I'm averaging about a gallon for every 1100 miles I drive. So many variables effect DEF use. I noticed it does burn more when I am towing. Top it off yourself, drive 2500 miles and see if it will take another 2.5 jug.
 

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DEF Usage

I'm averaging about a gallon for every 1100 miles I drive. So many variables effect DEF use. I noticed it does burn more when I am towing. Top it off yourself, drive 2500 miles and see if it will take another 2.5 jug.
I topped it off with a full 7 gallons, at just over 1500 miles my "Action Required" notification came on said 500 miles left. I added 5 gallons, at just over 1200 miles, the same notification came on. I have just over 14000 miles on my 2019 Denali Duramax 2500 now so I'm thinking I have a real problem but GM is saying normal usage. Is there anything I can do?
 

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I'm averaging about a gallon for every 1100 miles I drive. So many variables effect DEF use. I noticed it does burn more when I am towing. Top it off yourself, drive 2500 miles and see if it will take another 2.5 jug.
I topped it off with a full 7 gallons, at just over 1500 miles my "Action Required" notification came on said 500 miles left. I added 5 gallons, at just over 1200 miles, the same notification came on. I have just over 14000 miles on my 2019 Denali Duramax 2500 now so I'm thinking I have a real problem but GM is saying normal usage. Is there anything I can do?
Is your def usage more than 2% of fuel usage?
 

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Yes, it's more like 3 to 3.5%.
Am I reading this right?

You get 1200 mile on 5 gallons of def?

Which implies 1200/5 = 240 mpg (of def)

and that's 3.5% of fuel

so 240 x 0.035 = 8.4 mpg of fuel.

(Then to check 1200 miles/8.4 mpg -- 143 gallons of fuel
and 5 def / 143 fuel x 100% = 3.5%)
 

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Found your forum, time to vent about DEF use. I'm at 18,000 miles in a 2019 Silverado 3500HD dually. Ran load at 12 mpg. Ran unladen at 18 mpg. Speed 70 mph. 268 mpg of DEF.

I drove 5300 miles on a round trip to Kentucky (empty-no trailer), picked up my new gooseneck, up to Illinois(empty), picked up payload (trailer/load 15000 lbs), drove through Iowa and back to California. In 5100 of those miles I used 19 gallons of DEF.

Dealer said they want to monitor my DEF use over the next month while driving around town and so called fishing trips. I told them I didn't buy a dually for use as a grocery getter. And by the way, they wouldn't rotate my tires for my first visit to them. Already performed two oil changes elsewhere prior to dealer visit.

I'm about ready for yellow side boards on my bed with some verbiage. Really like my truck otherwise.
 

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After a week in the shop, my local dealer hasn't done anything about my excessive DEF usage, says GM hasn't issued a reprogram fix for it yet. In the Owners Manual, it says you should get "several thousand miles" on a tank of DEF, my tank is 7 gallons. It also says there should be 3 notifications; mine goes straight to "Action Required, add DEF now". Also, it seems to me if so much DEF is injected into the system, it has to be damaging other parts. And I know my fuel mileage has decreased since the DEF usage has increased. It's time for everyone who has this issue to call GM Customer Relations at 800-222-1020 and voice your concerns and disappointment about their reluctance in getting this problem resolved. It seems they did a recall for the 2017-2018 Duramax models but aren't extending it to the 2019 models yet.
 

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The person you were talking to is full of of crap.

Programming won't be different on 20% of them.....


(if there was a programming change, then it would be vehicles before a certain build date (or serial number) not a random 20%)
Not so, it seems to be a random number of trucks--I've talked to owners of 2019 trucks who go service to service (7000+ miles) before adding DEF, and others who are using like mine, 1500-2000 miles per 7 gallon tank.
 

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2017, 2500HD, LTZ, front guard, Duraflap mudguards, Leer bed topper
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Anyone consider reporting this problem to EPA? Hey, figured we could all use some levity... the Gov, “helping”...
 

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Just reading this thread now as I had an interesting DEF episode the other day. I’d been pulling my fifth wheel around Southern Colorado/Northern NM. Lots of engine breaking and three passes ranging from 9-11000 feet. First long trip with L5P so I checked regularly and it always stated DEF OK. Also, Being the first long trip, I filled the def before I left and ran a trip meter on it. At 1500 miles I get Def low message with the reduced speed threat. Took the first exit to buy some fluid and while idling it jumped around to different messages of increasing severity. I added 5 gallons. Maybe could’ve taken more, so it was indeed low. My concern though, is where the hell were the 1000 and 500 mile warnings? With my LML I’d add DEF at the 1000 mile warning, and it lasted forever.

I


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Just reading this thread now as I had an interesting DEF episode the other day. I’d been pulling my fifth wheel around Southern Colorado/Northern NM. Lots of engine breaking and three passes ranging from 9-11000 feet. First long trip with L5P so I checked regularly and it always stated DEF OK. Also, Being the first long trip, I filled the def before I left and ran a trip meter on it. At 1500 miles I get Def low message with the reduced speed threat. Took the first exit to buy some fluid and while idling it jumped around to different messages of increasing severity. I added 5 gallons. Maybe could’ve taken more, so it was indeed low. My concern though, is where the hell were the 1000 and 500 mile warnings? With my LML I’d add DEF at the 1000 mile warning, and it lasted forever.

I


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'DEF OK' message is given until the tank is about the 30% level.

My '18 gives the 1000 mile warning in the range of 20 to 22% on the def gauge. (when being used for non-towing duties)

I've taken it all the way to 'empty' just to see how it reacted.
There should be a thread on here with my observation details....

but as I recall it was the 1000 mile warning once, the from 300 mile remaining a 'miles to empty' message every time it was restarted.

When it gets to empty the first speed limit warn screen and mileage countdown comes on and cannot be cleared.
This screen as a countdown of the '500 miles to 65 mph limit')

I've been filling it at a bulk dispenser so that I can fill it and know how much def used, without having to mess with guessing how much is left in a part jug used to top off.
 

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I just stopped and did bulk. I had 1750 miles and put in 4.7 gallons. Most of that was towing my fiver. I’ll keep an eye on it, recording the amount and miles. Just seems like a lot to me.


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Man I hate to see this stuff. I am debating selling my LBZ because I am seeing spots where it is going to start rusting out but posts like this among others are making me think on either keeping mine and letting it rust or switching to HD gas and not worrying about my exhaust pipe sidelining me on vacation
 

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Not sure why mine skipped some critical warnings, but doing some math I’m at about 3% of fuel consumption. Lots of headwinds, high altitude and hard climbs on this trip. Trip isn’t over yet, but I’m back on the flats of Texas, so we’ll see what happens.

I sure wish truck had a def gauge like those other manufacturers. My Edge used to give a percentage on my LML, but with this engine that option isn’t there.


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I traded my 2021 Denali in with just over 11,000 miles. I could almost go 250 miles per gallon of def, 6 times the amount of my 2014 as it would use 9 gallons for that mileage.
 
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