when adding def how do u know its full? when it overflows or is there a warning or something? thanks in advance:)

Add when the message is displayed , then add if i recall(??) the owners manual add 13 litters, other than filling when the message is displayed its a guess. there is no warning etc.

If you are doing it in a relatively quiet place, it's easy to hear the gurgling sound change as the neck starts to fill. If you do continue to fill it, there is an overfill "cup" around the fill tube that will collect any excess. 7 1/4 gallons will fill it from completely empty (truck restricted to 55mph) to completely over flowing. (Did it once just to see) If you put in the typical 5 gallons when the warning comes on, you won't have to worry about over filling and should be good for roughly another 5,000 miles.

If you are doing it in a relatively quiet place, it's easy to hear the gurgling sound change as the neck starts to fill. If you do continue to fill it, there is an overfill "cup" around the fill tube that will collect any excess. 7 1/4 gallons will fill it from completely empty (truck restricted to 55mph) to completely over flowing. (Did it once just to see) If you put in the typical 5 gallons when the warning comes on, you won't have to worry about over filling and should be good for roughly another 5,000 miles.
NO NO NO NO NO!!!!!!!!
Fill your DEF tank until you get the first spit back of DEF from the tube, thats it, no more.
The DEF tank will hold more than the 5.3 gallons advertised. DEF freezes so if you overfill the DEF tank and the DEF freezes, it will expand and damage the tank.

NO NO NO NO NO!!!!!!!!
Fill your DEF tank until you get the first spit back of DEF from the tube, thats it, no more.
The DEF tank will hold more than the 5.3 gallons advertised. DEF freezes so if you overfill the DEF tank and the DEF freezes, it will expand and damage the tank.

Hmmmmm. My owners manual doesn't say anything about spitting back.

I will fill mine to the top and worry about freezing when it happens.:)

if you go on the gm site in the about def area it talks about def and freezing @12 degrees and also says not to fill tank completely because of freezing so unless you live in so cal. like me i wouldn't do it

if you go on the gm site in the about def area it talks about def and freezing @12 degrees and also says not to fill tank completely because of freezing so unless you live in so cal. like me i wouldn't do it
IF you are in an area that freezes then there would be a small concern. Small because unless you are topping off the tank everyday, it will only be full for a short while. So it would have to get to 12 degrees for awhile when the truck is NOT running right after it was filled to the brim. A little awareness of what you are doing and when/where you are doing it can go a long ways in avoiding many problems. This is one of them.
Use your head and take advantage of the 7+ gallons the tank can hold or not....It's your choice

I'm not saying I won't use the full space I just saying if I lived in a cooler climate I wouldn't do it during the winter. I live in so cal where if it hits 40 degrees it's considered a cold snap I mean it was 93 today so ya

NO NO NO NO NO!!!!!!!!
Fill your DEF tank until you get the first spit back of DEF from the tube, thats it, no more.
The DEF tank will hold more than the 5.3 gallons advertised. DEF freezes so if you overfill the DEF tank and the DEF freezes, it will expand and damage the tank.

I ran it completely out and filled it completely up just to get a feel for the range and exactly how much the tank would hold. I was in Las Vegas in the middle of a trip when I did it. 5 minutes after filling it, I drove 850 miles pulling 21k lbs, I wasn't too worried about over filling the tank or freezing. ;)

how far did you get on a full tank?

Moved to Maintenance & Fluids.