You'll get about 7500 miles per tank of DEF. That's roughly 5.3 gallons.

30% means you'd still have about 2000-2500 miles before you had any low def issues.

I used to wait until the 300 mile warning, and then added 2.5 gallons. 3000-ish miles later, repeat...

 

I don't remember how much it was at the dealer, but before I deleted they were gonna add some while I was having the oil changed and it was a lot higher than what you would by at Walmart or an auto zone. I only bought 1 container of it and that was at Walmart and I had put 5000 miles or so on it before getting the add def message. I'd say just add when it tells you to, or fill it up before going on long trips so that would be one less thing to worry about.

 

Add itwhenever you want, there is no mystery to it. It's just like windshield washer fluid or fuel in your tank, sometimes you fill it when it's half full sometimes you're almost out until you fill it. You're not going to hurt the trucks feelings if you put it in before it warns you it's running low. Most people, myself included, add 2.5 gallons when the 30% remaining message comes up, that way you know there's room for 2.5 gallons.

 

You're not going to hurt the trucks feelings if you put it in before it warns you it's running low.

IMHO a lot of the "DEF Quality Poor" messages people have been very verbal about around here are a result of constantly filling the DEF tank versus consuming what's in there and only filling it when it needs filling.

DEF has a shelf life, and filling it when there's still potentially very old fluid still in the tank just dillutes the old fluid more and more with a bit of fresh stuff. Repeat enough times and I don't find it coincidental that the DEF quality poor messages start to pop up.

I agree with others - when the low indication comes on, add fluid then, not before.

 

Part of the pre-delivery services is to FILL the DEF tank! Obviously, they did not do what GM paid them to do. If they refuse to do maintenance during the two years (which GM will pay them to do), ask them if they would like sit down with you and a factory representative to discuss a dealer's obligations under GM's covered maintenance program.

 

Id add more DEF when I got the 1st warning.

 

This has been beat to death but . . . DEF has a shelf life. You want to try and cycle old DEF out of your tank and replace with new (fresh) DEF. Even GM literature that you received with the truck tells you this. You don't want to stock up on it and leave it sitting around for a long time. They say to store it in a cool dry place too. So if you keep a jug in your truck in the summer heat and your truck its 110 inside that probably isn't very good for it either. Just and FYI > > > one more time.

 

The way I run mine as advised by a trusted GM tech is this:

Run until it nags low

Add 5 gallons (2 2.5 gallon jugs) of DEF adding the last jug slowly to avoid burp mess.

It is not recommended to "keep topped off" or add small amounts mid tank.

 

^ This.

I buy the DEF (two 2.5 gallon jugs) when I get the first warning and keep it in the bed. I continue driving through the subsequent warnings and until I see Al Gore chasing me in the rear view mirror. Right about the time he seems like he's about to grab on to my bumper and stuff a potato in my tailpipe, I add both jugs.

 

I continue driving through the subsequent warnings and until I see Al Gore chasing me in the rear view mirror. Right about the time he seems like he's about to grab on to my bumper and stuff a potato in my tailpipe, I add both jugs.

:hehe::hehe::hehe:

 

I am going to be taking delivery of my 2015 Duramax LTZ in a couple of weeks...This will be my 4th Duramax since 2009 but my 3 rd that required DEF... I personally like to add. 2.5 gal when I get the 1000 mile to empty warning and I have never had any DEF related issues.


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I have been adding every 3000 to 4000 miles - with my issues I think I will wait until I get the "Low level 1". Don't want to hit level 6.

Warning Level 1
Warning Level 1 is triggered when the DEF level falls below the top-most position of the DEF Level Sensor and the estimated range remaining is greater than 1609 km (1000 mi). No prompts or warnings are presented to the driver.

Warning Level 2
Warning Level 2 is triggered when the estimated range remaining falls below 1,609 km (1,000 mi) based on current DEF consumption rates. The Driver Information Center (DIC) displays the message Exhaust Fluid Range X MI, where X is the estimated range remaining in miles. This message remains on the DIC until acknowledged by the driver.

Warning Level 3
Warning Level 2 automatically advances to Warning Level 3 when the ECM detects an ignition ON to ignition OFF event. A level 3 warning remains active as long as the estimated range remaining is greater than 644 km (400 mi) based on current DEF consumption rates. No prompts or warnings are presented to the driver.

Warning Level 6
Warning Level 6 is triggered when the estimated range remaining is less than approximately 0 km (0 mi) based on current DEF consumption rates. The driver will hear 4 chimes on entering Warning Level 6. The DIC displays the following messages:
• Exhaust Fluid Empty Refill Now
• 89 km/h (55 mph) Max Speed Upon Restart
The messages are also displayed at the beginning of each ignition cycle. The Exhaust Fluid Empty Refill Now message remains on the DIC until acknowledged by the driver. The 89 km/h (55 mph) Max Speed Upon Restart message is not acknowledgeable.
At the next ignition ON event, the system will advance from Warning Level 6 to Warning Level 7. If fuel is added to the vehicle without an ignition cycle the system will advance to Warning Level 8.
In the event of a refill, the scan tool may show that fluid has been added, but the vehicle may not release from the warning level unless it is driven for greater than 6 mph (10 km/h) for approximately 5 minutes.

 

I think you mean level 2 -- which is when you the 1000 mile warning occurs.

Mine won't hold 2 jugs even at the 300 mile remaining warning, so like ctdmax I've adopted the 1 jug at the 1000 mile warning method.

 

I let it get down to about 200 miles and then added 5 gallons. Took all of it without any issues.
Rich

 

My 2015 work truck had the 29% message pop up at 700 miles on the truck. I added two jugs, 5 gallons of def fluid and it was full. So much for dealer pre-delivery. Oh and by the way, not one grease fitting was touched by the dealer either during pre-delivery!

 

My 2015 seems to use more DEF than previous years reported usage, but I don't know for sure. I added 6 gallons the last time I filled when my truck was warming me 500 miles. I am pretty sure the tank would hold 7 gallons. I was just satisfying my own curiosity when it swallowed the first 5 gallons. I'll probably run mine down to the 500 mile mark, then add 5 gallons because it's easy with the 2.5 gallon jugs.

I do oil changes at 5k intervals, so I may try and do the same at those intervals.