3.0 Duramax DEF consumption

Firetrout · January 27, 2020

What are yalls thoughts on DEF consumption? I have 9400 miles on mine and have added 15gal so far and am at half tank right now. 80% of driving is hwy. Thoughts?

yousaveone · January 27, 2020

Mostly highway no towing, I burn 1 gallon per 1000 miles. The manual says if you tow it will use a lot more fluid. How much weight do you have in the truck?

redwngr · January 27, 2020

Do you know that it was full at the start of the 9400 miles?

I don't have much faith in the def gauges other than to get a guestimate.

What is you average fuel mpg over those miles?

DEF is used whenever a diesel is running. Use is proportional to fuel used. More fuel requires more def.

GM published that they expected the 6.6 to use about 1.5 to 2 gallons of def per 100 gallons of fuel (1.5 -2 % of fuel usage).

If 3.0 ratio is the similar, then expected def can then be worked out from average fuel usage.

9400 miles at 25 mpg

9400/25 = 376 gallons of fuel

2% = 7.5 gallons of def.

srqG8 · January 29, 2020

Going by my DEF gauge (FWIW), I’ve used about 1.5gal (if each “bar” is worth 0.5 gal like I think I read in the diesel owner‘s manual insert). About 4200 miles on the odo, avg 25 MPG over those miles. If this helps: No towing yet, 60% hwy/40% city, very little idling.

Haven’t added any DEF yet, but will soon.

wizard4878 · February 8, 2020

sounds really high to me. I drive a semi getting 6mpg and only need about 4 to 5 gallons a week. using that much I would think your dpf is close to being plugged up. I'm just going off my experience with 13 and 15 liter Diesels though, so take it for what its worth...

yousaveone · February 8, 2020

After 3000 miles I added 2.5 gallons and it shows full on the gouge. Was one bar under 1/2 when I added it.

Matt076 · February 11, 2020

I tow a 5000 lb. snowmobile trailer to Michigan and back. The trip is roughly 1100 miles round trip and I use between 15 and 20 gallons. What could the problem be? Sometimes the 500 mile warning will come on when I still have a half tank of fuel left and I fill them up at the same time. If this is normal then I need a bigger def tank or a bigger bed to haul fluid in . lol I am not a happy camper by any means. Goes to the dealer again tomorrow. However they really have no insight into this issue!

ChuckTaylor · April 11, 2020

How is the DEF usage looking on these trucks now?

becker87 · April 12, 2020

I have about 10,000 miles on mine. Probably just over two tanks of DEF. Minimal towing and hauling but mainly rural roads and around town

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Chrisd534 · April 13, 2020

On 4/11/2020 at 12:12 PM, ChuckTaylor said:

How is the DEF usage looking on these trucks now?

3000 on mine and only one notch of the DEF bar gone.

davidr83 · April 13, 2020

When I got mine (Feb. 27th), it had less than 10 miles and the def was about half full. I had to fill the def(2.5 gals) up at about 2300 miles and it's still showing the same amount of def since then and I'm a little over 2650 miles now. 70% highway/30% city driving usually running 5-10 over the speed limits and have not towed anything but did have the bed full of stuff a couple times.

LaRed · April 13, 2020

Bought late January. I have 5700+ mi on mine. DEF tank full when I left the dealer. First 4300 mi. DEF gauge showed 1/2 tank remaining. No towing practically all highway mi. Thought I should have plenty to make a 1250 mi trip home from FL pulling my 20 ft Flats boat based on history. After 200mi. DEF warning 1000 mi remaining still only 1 bar under 1/2 tank. 2 1/2 gallons of Blue DEF from WalMart put it back to 1 bar under full. 50 mi from home warning came on again.... 265 mi. remaining. This was shocking. Another 2 1/2 gallons of Blue DEF from WalMart put the gauge back to 1 bar under full.

So..... not sure how much I'm burning. But I do expect the gauge to be more accurate. This does seem to be excessive to me. Maybe its not. Based on the gauge it seems certain I burned at least 2 1/2 gallons in 1000 mi. while pulling the boat.

Overall fuel mi including the tow home 21.3. Towing the boat only ..15.1 for the 1250 mi. trip to NW Arkansas. Overall before towing 22.7.

Edited April 13, 2020 by LaRed

topgear1224 · April 18, 2020

I have 2400 miles and showing 180miles remaining...... Def is 15.28/ GALLON up here.......

That's .04/mile in DEF. Or based on my 24mpg avg and extra 0.96 per gallon of fuel used.....

Diesel is $2.70 +$0.96 in DEF.

This damn thing is $3.66/gallon to go 24 miles.
15.25¢ per mile....

The 6.2L is 12¢(19mpg combined) per mile WTH.

Dealer told me should only need filled when the oil is changed.....

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steve841 · April 18, 2020

48 minutes ago, topgear1224 said:

I have 2400 miles and showing 180miles remaining...... Def is 15.28/ GALLON up here.......

That's .04/mile in DEF. Or based on my 24mpg avg and extra 0.96 per gallon of fuel used.....

Diesel is $2.70 +$0.96 in DEF.

This damn thing is $3.66/gallon to go 24 miles.
15.25¢ per mile....

The 6.2L is 12¢(19mpg combined) per mile WTH.

Dealer told me should only need filled when the oil is changed.....

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You're either paying too much or messed up your math.

DEF is around $15.00 per 2.5 gallons.

topgear1224 · April 18, 2020

You're either paying too much or messed up your math.

DEF is around $15.00 per 2.5 gallons.

Have to use ACDelco fluid from the dealership otherwise the dealer will not submit any DEF claims under warranty when everything fails because it gets to -40 degrees out here. Going form a 70 degrees humid garage (from ice melting) to -40 causes condensation in the DEF tank.

15.28/gallon here. 26.55/ 2.5 gallons.

Using the per gallon to cover labor.

If you have an issue without a service ticket your SOL.

2 L5P last winter went through $6k in out of pocket repairs each at 5k miles dealer claims it was because of the supertech fluid being contaminated with water. dealer called GM. GM asked if they use genuine fluid dealer said no and GM said they're not covering anything. apparently there is a bulletin out that states that any 2007 and newer Duramax must use AC Delco genuine fluid.

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EDIT: BULLETIN DOES NOT OFFICIALLY EXIST.