How much DEF to add?

About 50% is a good rule of thumb.
Edit.
I misunderstood. Don't worry about it it's not your truck.

 

This is dangerous. Some jack ### will folllow your advice. So for you out there that don't know better this is a JOKE.

I'm going to record this as my monthly mandetory near miss report for my safety department.

 

Had a guy do just that on a job. Mechanic had to drain tanks. You guessed it. FIRED!

 

These crack me up.. but these really are dangerous posts. Some poor driver, maybe not even a Swift driver, just a noobie.. might not know what DEF is then GOOGLE "DEF", come across this article, and think they just learned something new. So I'm going to be the downer, and say out loud for the new guys.. DO NOT PUT DEF IN YOUR FUEL TANK. DEF GOES IN THE DEF TANK ONLY!!!

 

It's the same ratio used for the blinker fluid.

 

I’m with you and the other one.
This thread really should be deleted.

 

but in an emergency you can pee in the Def tank........ that's when you're in a def jam

 

i would hope...none.

 

After the fuel shuts off you can top it off the rest of the way with DEF. That's why pumps are setup to pump the fuel first.