DEF can I drain the tank?

Eastwood

New member
15
5
I just bought a new 2021 GMC Sierra 1500 Denali 4x4 crew cab and really happy with the power the 3.0 diesel has. I'm concerned about the def fluid since I rarely put over 7,500 miles on my vehicles per year. Is there someway to drain the def tank on the truck so that I can put fresh def fluid in if needed?
 

OH Chevy Diesel

New member
28
7
Not sure but you may be able to siphon it out. Then put a fresh bottle in it. I don’t know if they have an anti-siphon valve on the DEF tank but I doubt it.
 

Firefly

New member
2
2
Year
2021
I’m in the same boat as you with how many miles I will put on in a year and was wondering the same thing
 

gemarsh

Nebraska, where the Dusty Denali Diesel's roam.
Staff member
500
232
Nebraska
Year
2021
Yep, here's a economical harbor freight option:
I am thinking that device won't work too well. The solid black tube is the inlet to the pump.

I haven't looked, but it would take some mighty flexible hose to get from the filler neck all the way over to the passenger side of the frame, where they mounted the def tank.
 

BoostN

Administrator
Staff member
359
71
TN
Year
2021
I am thinking that device won't work too well. The solid black tube is the inlet to the pump.

I haven't looked, but it would take some mighty flexible hose to get from the filler neck all the way over to the passenger side of the frame, where they mounted the def tank.

Good point! I didn't think about the routing underneath.
 

MNTIM

New member
24
5
I will have to crawl under it tomorrow and see if I can find a drain plug
I’ve looked as well with the same concern. Worst case is drop the tank or try and get some real small hose all the way to the tank from the filler.
I havnt been able to find a schematic for the stuff (pump maybe?) mounted under the cover on the bottom of the tank to see if that’s a easy way to drain.

ive always made sure I buy super fresh def. usually find a box that’s no more than a month old. And in the summer I don’t drive it daily so I will get the level down to 10-15%. Then fill it before or around winter.

any time def is over 80 it will slowly start to degrade and less that 60 it has a 2+ year life span. so winter I’ll have it full with no risk of it going bad. And summer I maintain a smaller amount.
Keep in mind if I was to take my boat or any trailer 5-6 hrs away. I wouldn’t leave at 15%.
Over the past 10k now I average 1000mpg for empty driving
500mpg for towing my small trailers and boat.
Overall ive used 8 gallons in 10k miles
 

rbdjr

Active member
110
41
NW New Jersey
Year
2021
Bought my truck 2021 RST 3.0 at the end of June, have a bit over 7000 miles now, added 2.5 gals at my free oil change provided by the dealer at 3000 miles.
it still at one notch below half, many days over 90deg plus? and the def is no good now??? seems weird, I also can't find any drain on my DEF tank?
I think I have used just around 3 gals in 7000 miles I guess.
 
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