2013 CTD - I'm getting around 700 MPG for the DEF while towing. Just added some for the first time last week.
When I got my truck, my salesman relayed a message from the diesel mechanic at the dealership. He cautioned me not to let DEF sit in the tank for very long, and said it crystallizes and causes problems. He suggested running the DEF low - down to a gallon (approx 1/4 tank) remaining before adding more, and then only add a gallon at the time. Has anyone heard anything about this? I can't find any information to substantiate it. Besides, if it gets old, or crystallizes in a short period of time, how can it be sold in containers?
I did, however, notice that when I filled up with DEF (at a truck stop pump), that residue around the pump handle was crystallized. According to this
document it has a shelf life of one year. Anyone have problems with their DEF crystalizing?