DEF: Fill When Low or Top Up?

[JOHRY]

Just curious as to what is best.

I know the Service Manual says to fill the DEF when you do an oil change. I'm just wondering if this is by design (to prevent stagnant DEF from lingering in the system).

Is there any issue with throwing in a new jug when it gets to 2/3 and keeping it full?

 

[Travelin Ram]

It’s entirely a preference. Realistically it’s never going bad. It’s just urea in water.

 

[mtnrider]

It’s entirely a preference. Realistically it’s never going bad. It’s just urea in water.

It will go bad, DEF has a shelf life of 1 year if stored properly. In hotter climates it could last less then that. Realistically he will go through that in a year but saying it will never go bad is not true.

OP, I usually run my 6.7 down until the light comes on or close to that then I add a 2.5 gallon jug (this is a 6.7), I never keep it "topped off"


.

 

[WY-Dave]

The tank on mine is 5.5g I think the 5th gen is abit bigger. When you see the level at 1/2, then put in a 2.5g jug. This way in theory, there will always be 1/2g of space in the tank and you won't ever overfill. And just before winter (just a time hack) I let it run down till the light comes on to "flush" the system.

https://www.peakhd.com/lifeblood/fluid-thinking/a-guide-to-def-storage-contamination/

"The best temperature for storing DEF is 77°F. Higher temperatures will not affect the quality of the DEF, but will impact its shelf life. The quality of DEF also is not affected if the fluid freezes. When stored under optimal conditions — between 12°F and 86°F — DEF has a shelf life of up to two years. If stored in warmer temperatures, shelf life decreases."

And I have been using the WallyWorld DEF for 28k miles and Jan will be 2 yrs without a hickup. WW DEF flies out the store so I don't have to worry about being old.

 

[Burla]

Why buy DEF, just **** in that tank? DEF = Urea

Definition of *****...

Cellular metabolism generates many by-products that are rich in nitrogen and must be cleared from the bloodstream, such as urea.......


So this is great, ruin modern diesels by requiring them to be a mixture of **** and fuel. It is a matter of time before liberals will add def to the fuel itself, lol.

 

[HDGoose]

...

So this is great, ruin modern diesels by requiring them to be a mixture of **** and fuel. It is a matter of time before liberals will add def to the fuel itself, lol.

Only libs like clean water and air? I remember rivers burning and wells contaminated by irresponsible American companies. They put profits above the environment.

 

[Burla]

So DEF cleans your water, hmm. Or does it poison your water?

 

[Burla]

There is good news from a historical perspective, even during a point and time when this beautiful earth supported the largest o2 breathing animals walking around in history, the "air quality" was much worse in the terms that most people today are hysterical about. It turns out the burning of fossil fuels doesn't even move the needle when you look at a historical perspective and earths health. Today the co2 levels are right where the lowest co2 levels are in the historical graph, today between 400-500ppm. The good news is in 60 years or so, mankind will have to find something different to be hysterical about because fossil fuels will be gone.

My apologies for using the word liberal, I was really just laughing at DEF as a solution to save us.





If you were worried about n2o, despite all of the use of diesel without DEF, As of 2010 pre DEF, it was estimated that about 29.5 million tonnes of N 2O (containing 18.8 million tonnes of nitrogen) were entering the atmosphere each year; of which 64% were natural, and 36% due to human activity. So once again, follicle fuels will be gone soon enough, but the air quality will not change much in any sort or fashion. Meanwhile, I just had a friend lose his job of delivering trusses because the owner couldn't afford the DEF conversion of his fleet. Lots of pain and loss for something that wont even show up in the blip of history. They had 3 trucks and an additional machine that needed to be retrofitted, the owner could only afford 1 truck. Most of his employees were fired, despite his trucks bought new in 2004/5.

 

[RAM DRVR]

I put a jug in when I get to about 1/3rd tank. Never matches up with oil change.

 

[bill-e]

When I get to 1/4 tank I put in a 2.5 gal jug of Blue DEF. My thought is that this process cycles the DEF out faster. I'm comfortable with the quality of Peak Blue DEF, even more so now that I know that they warrant it and repairs required to your DEF system for 90 days, but I have no control over what happens in the tank in the heat of summer.

No matter what your preference, in the winter don't fill the tank as DEF freezes at 12°F so you need room for that.

 

[Iceclimber]

Why carry extra weight around.

 

[retired]

Why carry extra weight around.

not like def at 9 lbs a gallon should have much effect on a HD truck...

 

[Iceclimber]

not like def at 9 lbs a gallon should have much effect on a HD truck...

My man, I strive for peak efficiency. Besides I am a boat owner with 2 x 100 gallon fuel tanks. I run everything close to empty. In all seriousness, it doesn't matter if you run your def tank full not full whatever makes one happy.

I hope this isn't one of those forums where people spend their time picking at other people's posts and honest opinions. Because that is really annoying.