When to refill DEF tank

[BobsArmory]

So I have heard three different approaches to filling your DEF tank on Diesel Trucks.
For example, a person like me with a 5 gallon DEF tank takes 6 to 7 months to empty the tank:

1. Refill only when near empty and only put in the minimum amount to assure that you always have the freshest DEF possible.
2. Keep the DEF tank topped off as much as possible to reduce the air space in the tank thus reducing the possibility of crystallization inside the tank itself.
3. It really doesn't matter, fill it when ever you feel like it.

Thoughts?

 

[GON]

So I have heard three different approaches to filling your DEF tank on Diesel Trucks.
For example, a person like me with a 5 gallon DEF tank takes 6 to 7 months to empty the tank:

1. Refill only when near empty and only put in the minimum amount to assure that you always have the freshest DEF possible.
2. Keep the DEF tank topped off as much as possible to reduce the air space in the tank thus reducing the possibility of crystallization inside the tank itself.
3. It really doesn't matter, fill it when ever you feel like it.

Thoughts?

Reading points to geographic location being part of the equation. If you are in an area that the truck gets under freezing, a non full DEF is recommended by some.

Now being marketed and sold at some auto part retailers is a "premium" DEF. No sure if it is truly premium or just marketing. If your use if DEF is minimal, if the premium DEF is in fact better, might be something to look into for your use.

https://www.motorcraft.com/content/...st_Fluid/DEF Shelf Life and Fluid Quality.pdf

https://www.fordtremor.com/threads/blue-def-vs-blue-def-platinum.6226/

 

[BobsArmory]

From what I hear the "premium" DEF has a small amount of surfactant to help prevent crystallization.

 

[KrisZ]

I would top it off every oil change.

Just googled def treatment and of course we have them for def now. Maybe try that?

 

[OneLonelyBurrito]

I would be in camp fill it up when its low, it shouldn't really matter how or when you fill it up as long as you aren't letting it sit for super long periods of time like over a year. Basically all of the problems with DEF/SCR systems aren't related to how you fill it up the DEF tank.

 

[KrisZ]

I would be in camp fill it up when its low, it shouldn't really matter how or when you fill it up as long as you aren't letting it sit for super long periods of time like over a year. Basically all of the problems with DEF/SCR systems aren't related to how you fill it up the DEF tank.

DEF crystallization can definitely be a problem and it may be related to the DEF level in the tank.

 

[tnt_motorsports]

DEF definitely has a shelf life. If it takes you that long to go through a tank I’d subscribe to method 1. It’s easy enough when you are getting diesel to add DEF. All most all the truck stops I use have DEF at the pump. Add a couple gallons when it’s low.

As @GON said weather is definitely a factor if you live in a freezing environment.

Just my $0.02

 

[eljefino]

Today I learned that an additive has its own additives.

 

[Jetronic]

DEF definitely has a shelf life. If it takes you that long to go through a tank I’d subscribe to method 1. It’s easy enough when you are getting diesel to add DEF. All most all the truck stops I use have DEF at the pump. Add a couple gallons when it’s low.

As @GON said weather is definitely a factor if you live in a freezing environment.

Just my $0.02

the DEF tank on my dad's car lasts a whole year.

 

[OneLonelyBurrito]

DEF crystallization can definitely be a problem and it may be related to the DEF level in the tank.

Why do you think DEF crystallizing in the tank would be a problem? It will ultimately just get adsorbed into the new DEF it comes into contact with. That is something that is considered and tested long before diesels that required DEF entered the market.

 

[Donald]

I think many with a Ford PSD just wait for the "under 50%" notification and then add a 2.5 gallon jug. It will take the whole jug at that point. I do not stock up on DEF.

I often buy the DEF when I get the notification.

I have bought a lot of DEF at truck stop DEF pumps.

Maybe MATTD will comment on DEF additives. And/or premium DEF.

I buy the name brand DEF. But not premium.

 

[oil pan 4]

If you run it too low then your vehicle will only drive you to the nearest reeducation work camp.

 

[BMWTurboDzl]

What does your owners manual say? I would go buy that. I suspect you fill it every oil change or X# of oil changes.

 

[FreedomOne]

Why do you think DEF crystallizing in the tank would be a problem? It will ultimately just get adsorbed into the new DEF it comes into contact with. That is something that is considered and tested long before diesels that required DEF entered the market.

The injectors themselves get crystal build up and they are in constant use. Anything with a layer of def once exposed dries in to a white powder/crystal layer. Reabsorption depends on the how much it's built up.

 

[OneLonelyBurrito]

The injectors themselves get crystal build up and they are in constant use. Anything with a layer of def once exposed dries in to a white powder/crystal layer. Reabsorption depends on the how much it's built up.

Yes, the injectors get deposit formations, but those deposit will evaporate with temperature in the exhaust. The OEM's test for deposit formation on the injectors and mixer assemblies. Deposits on the injector and in the exhaust are a non issue as long as you get some temperature in the exhaust occasionally.

 

[FreedomOne]

Def injectors getting clogged is a common problem. Even my low mile Duramax had build up.

 

[thastinger]

Today I learned that an additive has its own additives.

Saving the environment...one 2.5 gallon plastic container at a time.

 

[johnmyster]

It doesn't matter. Fill/add when convenient, but make an effort to not have fluid in the fill tube during freezing conditions.

I buy at the pump. I don't deal with the silly jugs. I fill when low and if convenient. Low being relative to having big camper towing trips in the near future. My truck burns ~65:1 fuel to DEF. If weather is warm and I'm at the pump, I fill to the top.

Per my manual, in the winter, DEF in the filler tube can freeze and potentially bust the tube, etc. (That tube is over 6' long on our truck.) So in the winter, don't top off. It says at 1/2 on the gauge you can fit 2.5 gallons in the tank without having DEF in the fill tube. So when cold, buy 2.5 gallons when at or below 1/2. Even at 1/2, my tank has 3 gallons remaining, which is typically about 3000 miles worth. As such, this is easy to plan and do when convenient.

That said, DEF freezing point (12 deg F) doesn't happen here often, so it's easy to plan around if you did have big trips coming up and wanted to top off.

A little distilled water in the tank to reduce concentration is another way to help with in-tank crystallization.

 

[AP9]

Reading points to geographic location being part of the equation. If you are in an area that the truck gets under freezing, a non full DEF is recommended by some.

Now being marketed and sold at some auto part retailers is a "premium" DEF. No sure if it is truly premium or just marketing. If your use if DEF is minimal, if the premium DEF is in fact better, might be something to look into for your use.

https://www.motorcraft.com/content/...st_Fluid/DEF Shelf Life and Fluid Quality.pdf

https://www.fordtremor.com/threads/blue-def-vs-blue-def-platinum.6226/

Or, as I prefer to call it, DEF with trace contaminants

Diesel exhaust fluid, by definition, is 32.5% urea and 67.5% deionized water.

 

[tnt_motorsports]

A little distilled water in the tank to reduce concentration is another way to help with in-tank crystallization.

Be careful adding water. I’ve heard of companies moving to DEF quality sensors to measure the quality of the product in the tank / system. This would be one way to get a code on a new vehicle or piece of equipment.

Just my $0.02