I haven’t done any research on batteries, so can’t help you out.
I have been using the Walmart DEF so maybe your dealer may be right?? Got a better brand this time so will see how it works. I do know I was going to put DEF in my truck when it was around zero and it looked like a slurpy, lots of ice crystals in it. I held off til I got in warmer temps.
Yeah….the cold weather puts some extra stress on the motor with all it’s heaters. However, it seems to start with no problem when temps are around zero and not plugged in.
I usually leave Alaska the second week in November. Ran in more days of below zero temps this year than usual.
2016 3500 HD Durmax
1994 S and S 9.5' Camper (SOLD)
1999 S and S 9.5 Camper