DEF Tank, Top It Off or Run Empty?

[DeadEnd]

Looking for your best practices. My truck isn't my daily so it takes a good bit of time before I need to refill my DEF. Example, purchased truck end of January this year and just yesterday put a 2.5 gallon jug in it. Is it better to keep the tank on the fuller side (without overfilling) to reduce the amount of air and possible crystallization inside the tank or don't worry and just fill as needed when I reach 1/4 tank left?

 

[2001WS6]

I usually run it down to 1/4 left on the gauge and then put 2,5 gallons in. pretty much fills it.

 

[unclelala]

I usually run it down to 1/4 left on the gauge and then put 2,5 gallons in. pretty much fills it.

same here, heard somewhere to do that way to avoid error code? so been doing it that way since Sept. 2021 and so far so good.

 

[2001WS6]

same here, heard somewhere to do that way to avoid error code? so been doing it that way since Sept. 2021 and so far so good.

I learned the hard way. I believe the first time I filled my DEF tank it was half empty. I figured the 2.5 gallons would fit. Nope! overflowed.

 

[Blackpowder]

I do the same thing, dump in 2.5 gallons around 1/4 tank. On a recent road trip I let it drop below 1/4, and at 22% (from OBDmx monitor) the add DEF soon indication popped up.

 

[AH64ID]

If you are using a box don’t run it full, it’s too easy to overfill and have an issue.

If you use a pump you can run the pump until it clicks and not have any issues.

There is also average ambient temp to consider. DEF that is at 95° is only good for a few months.


Personally I use pumps and will top the tank off before a longer towing trip, or when it tells me it’s low. Even with our hot summers I burn enough DEF in 12-15K miles a year to not worry about it aging out.

 

[unclelala]

If you use a pump you can run the pump until it clicks and not have any issues.

almost 2 years of driving the ram Ive seen a pump once and that was in Michigan. I have not seen any in Ontario that I have seen anyway. Maybe at truck stops but they are far and few.

 

[AH64ID]

almost 2 years of driving the ram Ive seen a pump once and that was in Michigan. I have not seen any in Ontario that I have seen anyway. Maybe at truck stops but they are far and few.

I’m fortunate enough to have a pump only a few miles from work, which makes it very convenient for most my fill ups.

I have also been able to find pumps in small towns when I need DEF on a road trip.

 

[phatboy64]

Other then it being messy what “issues” happen if you overfill the DPF tank?

 

[jebruns]

I find I can dump in a 2.5 gallon box of DEF in at 1/2 tank, so that's what I do normally.

 

[jebruns]

Other then it being messy what “issues” happen if you overfill the DPF tank?

No issues other than the mess.

 

[Whiskey_Tango]

Other then it being messy what “issues” happen if you overfill the DPF tank?

Bad day if it gets into your fuel

 

[AH64ID]

Other then it being messy what “issues” happen if you overfill the DPF tank?

No issues other than the mess.

The sensor in the 19+ trucks have been known to throw a P203E when overfilled. There is a TSB on it.

From the TSB

DEF Level Sensor Operation:
The DEF level sensor is new starting in the 2019 Model Year. The new design level sensor uses an Ultrasonic Frequency (UF) signal to detect the proper fluid level. Previous model years use a radio frequency type sensor which operates differently, and can be less accurate.
In order for the UF level sensor to operate properly, it is crucial that there is sufficient air space between the top level of the fluid, and the top of the DEF tank. DEF tanks are specially designed to have an air space above the fluid, which is crucial for the level sensor to function. Without that air space, the UF signal cannot be returned to the sensor properly leading to a “No Echo” condition.

https://static.nhtsa.gov/odi/tsbs/2021/MC-10194039-9999.pdf

 

[phatboy64]

All good to know…..thanks!

 

[H3LZSN1P3R]

When it hits 1/4 tank dump a box in to get to 3/4 thats how i did it when i used DEF

 

[DeadEnd]

When it hits 1/4 tank dump a box in to get to 3/4 thats how i did it when i used DEF

That’s what I plan on doing. Do you think it’s better to keep the DEF somewhat topped off or is it just fine sitting for some months at 1/2 to 3/4 tank empty?

 

[AH64ID]

That’s what I plan on doing. Do you think it’s better to keep the DEF somewhat topped off or is it just fine sitting for some months at 1/2 to 3/4 tank empty?

It should be fine at 1/2 to 3/4 full.

 

[DeadEnd]

It should be fine at 1/2 to 3/4 full.

What about if its below 1/2 tank? Or am I way over thinking this? lol

 

[H3LZSN1P3R]

That’s what I plan on doing. Do you think it’s better to keep the DEF somewhat topped off or is it just fine sitting for some months at 1/2 to 3/4 tank empty?

You are fine at almost empty too you are over thinking it lol

 

[flan]

I run mine til the countdown comes into play then throw in a jug.