DEF Tank... Top off or run to empty?

WHISKEYSAVAGE

Tremor Fiend
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2022 F250 Lariat 6.7l
Seeing how it takes about 9 months to run thru a tank of Def, is it better to run to empty or top off with fresh Def? So the older Def can be diluted with fresh Def?
 
I've always just topped off with 2.5 gallons when the DEF gauges hits 3/4. I have no evidence to support my assertion, but I've always worried that if I run it down and there is more air in the tank that it would be more likely to form the DEF crystals and possibly plug the injector. I mean with more air in over time as it takes me quite awhile to use DEF as well.
 
I run it to 1/4 tank then add a 2.5g jug. So far no DEF related issues doing this, and my DEF use might be even less than yours.
 
Seeing how it takes about 9 months to run thru a tank of Def, is it better to run to empty or top off with fresh Def? So the older Def can be diluted with fresh Def?
I just add a 2.5-gallon bottle to mine once it gets below 1/2. When Ford does my routine service, they just top it off as well.
 
I'm in the "top it off" camp. Since the tank capacity amount is 7.5 gallons, that's 3/2.5gallon boxes...I just top off with 5 gallons of DEF.
 
My apologies for an off topic question but I see that everyone uses “jugs” to top off or fill their DEF tanks. I actually use my fuel station’s DEF pump to fill up when it’s needed. Am I missing something? Is the pump a bad idea and the jugs are much better to use for the health of our rigs?
 
My apologies for an off topic question but I see that everyone uses “jugs” to top off or fill their DEF tanks. I actually use my fuel station’s DEF pump to fill up when it’s needed. Am I missing something? Is the pump a bad idea and the jugs are much better to use for the health of our rigs?
I use the truck stop DEF pumps and no issues with my 2012 after 10-years. Much easier and cheaper than the jugs.
 
My apologies for an off topic question but I see that everyone uses “jugs” to top off or fill their DEF tanks. I actually use my fuel station’s DEF pump to fill up when it’s needed. Am I missing something? Is the pump a bad idea and the jugs are much better to use for the health of our rigs?
I don't live near, or regularly pass by fuel stations that have DEF at the pump, so jugs it is.
 
I've always just topped off with 2.5 gallons when the DEF gauges hits 3/4. I have no evidence to support my assertion, but I've always worried that if I run it down and there is more air in the tank that it would be more likely to form the DEF crystals and possibly plug the injector. I mean with more air in over time as it takes me quite awhile to use DEF as well.
I've read you're not supposed to keep your DEF tank full because the DEF freeze point is 32F and if you have this happen the tank can rupture. If you're truck will never see freezing conditions then top off.
 
I've read you're not supposed to keep your DEF tank full because the DEF freeze point is 32F and if you have this happen the tank can rupture. If you're truck will never see freezing conditions then top off.
Different points of view on this. Some say fill it and not worry about it, other references to filling to 60% in freezing weather. Here it is from the manual:

"FILLING THE
TANK IN COLD WEATHER
Diesel exhaust fluid may freeze if the
ambient temperature is below 12°F (-11°C).
Your vehicle has a preheating system
which allows diesel exhaust fluid to
operate below 12°F (-11°C). If you do not
use your vehicle for an extended period
when the ambient temperature is below
12°F (-11°C), the fluid in the tank may
freeze. If the tank is overfilled and the fluid
freezes it may cause damage that your
Warranty will not cover."

DEF expansion when frozen is 7%. (Same as water) So, if you keep your tank 3/4 full in sub-freezing weather, you should be fine. If the DEF freezes, it will recover and not harm the system, nor the DEF.

DEF does not go into the injectors, ever.

DEF System.jpg
 
As others have said : I don't have any fuel stations that I use on the regular that provide DEF through a pump.
 
Different points of view on this. Some say fill it and not worry about it, other references to filling to 60% in freezing weather. Here it is from the manual:

"FILLING THE
TANK IN COLD WEATHER
Diesel exhaust fluid may freeze if the
ambient temperature is below 12°F (-11°C).
Your vehicle has a preheating system
which allows diesel exhaust fluid to
operate below 12°F (-11°C). If you do not
use your vehicle for an extended period
when the ambient temperature is below
12°F (-11°C), the fluid in the tank may
freeze. If the tank is overfilled and the fluid
freezes it may cause damage that your
Warranty will not cover."

DEF expansion when frozen is 7%. (Same as water) So, if you keep your tank 3/4 full in sub-freezing weather, you should be fine. If the DEF freezes, it will recover and not harm the system, nor the DEF.

DEF does not go into the injectors, ever.

View attachment 115106
Because of the freezing issue I don’t top it off in the winter, nor just before the temps get cold.

As a rule I top off before long tow trips, Other than that I don’t worry about it much.
 
I've always just topped off with 2.5 gallons when the DEF gauges hits 3/4. I have no evidence to support my assertion, but I've always worried that if I run it down and there is more air in the tank that it would be more likely to form the DEF crystals and possibly plug the injector. I mean with more air in over time as it takes me quite awhile to use DEF as well.
I do the same.
 
Some folks say DEF goes bad over time. If that is true then I would say run it down if you don't use it much and top if off often if you do use a lot.
 
I've always just topped off with 2.5 gallons when the DEF gauges hits 3/4. I have no evidence to support my assertion, but I've always worried that if I run it down and there is more air in the tank that it would be more likely to form the DEF crystals and possibly plug the injector. I mean with more air in over time as it takes me quite awhile to use DEF as well.

Exactly what I do. If the gauge is just below the 3/4 mark it will take 1 - 2.5 gal jug to fill. We have a 500 gal on-road fuel tank at our yard and keep 10-15 jugs at all times for the trucks and equipment.

IMO less air in the tank is less chance of DEF crystals. I may be totally wrong on that but the truck won't run without out so I keep it full.

On a similar note - when do ya'll fill up? I'm a never let the tank get below 1/2. Usually fill up at 3/4 but the fuel is convenient.
 
Some folks say DEF goes bad over time. If that is true then I would say run it down if you don't use it much and top if off often if you do use a lot.
The question is "when" does it go bad and what is difference between new Def and 9 month old Def? Does the truck use more older Def to get the job done or does Def really not do anything when it gets old?
 
The question is "when" does it go bad and what is difference between new Def and 9 month old Def? Does the truck use more older Def to get the job done or does Def really not do anything when it gets old?
The best answer to this is that the DEF solution is critical. If there is heat involved, evaporation can occur and the solution changes. Here is a link with the best description I could find.


Also found this chart for a quick indicator.

DEF Shelf Life.JPG
 
When my DEF guage shows half full, I just add the Ford 2.5 gallon jug and it tops it off.

******If you buy DEF from anyone check the shelf life date. I had a Ford dealer try and sell me 2.5 gal container of DEF that was a year old. No go. I asked for a 2.5 gal jug that was less than a month old, he did not even know there was an expiration date. So he said…😏
 
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