At what temp will diesel fuel gel in our trucks?

My 96 seems to struggle to stay warm in the winter. The ebpv stays on while driving and the temp gauge barley reaches the n on normal. If the truck idles it will warm but not much at all. Is the thermostat stuck open?

 

Straight # 2 should be good down to 5 to 10 degrees. I'm running #2 with Howes antigel. It has been down to negitive 30 degrees, and I haven't had any problems. But I still have the fuel heater in the bowl. I would say the thermostat isn't working properly. I recently installed a new one it the 96 C&C, and it made a big difference.

 

I hope I don't have any gelling issues in the morning.

 

Mine was outside last night with well bellow 0 temps. #2 and 2 stroke oil and she wasn't gelled. Fired right off. No fuel heater either.