Ok so from what I understand DEF freezes at approx 23 degrees, a nice day in Montana. The manual states do not overfill the DEF tank due to freezing. So when you park the truck say 20, 30, 40 below or even at the balmy 20 degrees and the urea tank freezes solid does is still start and run do you have to sit and let it idle till the heaters melt the tank ?? I wouldnt think the heaters would work when the truck is not running. There are times you can not plug a truck in. Just a question I have'nt found the answer to.

 

DEF does not start to freeze/crystallize until 12° F (-11° C). Even then it becomes more of a slush then a frozen mass. For it to freeze solid would take a couple of days or more at temps of -20° F (-25° C) or lower. The reason Ford warns not to over fill the tank is DEF expands as it freezes and will crack the tank.

As for the heating system... It is only active while the vehicle is running and will thaw out the DEF in short order. The EPA also allows what they call a period of non-compliance to give the DEF time to thaw out, so even if it is frozen solid it is a non-issue and you can drive as normal.

It should also be noted that Ford's DEF supplier (Terra Environmental) has a winterized DEF about to hit the market that stays liquid down to -22° F (-30° C).

 

Great information!!!! Thank You PowerstrokeHD

 

the current info I have also matches the above stated

 

I went to a powerstroke seminar today and heard the same things except for the winterized DEF. Have you heard what they use to winterize it? Will it effect emissions?
From what they said today it will be only water and nitrogen coming out of the exhaust. Performance will be better and mileage will be a lot better. Rep said the truck throws you back into the seat.
380+ hp and 750ftlbs torque. John

Oh, And I got cool camo powerstroke hat and a powerstroke nerf football. LOL