At what temperature do you idle no matter what, even if you have an apu

Def does freeze up but your truck has coolant lines running to def system and it'll thaw it out when truck is running.
If I gave treated fuel I can shut off my truck and it's good to -15f but I wouldn't risk it without having spare filters and diesel 911 handy

 

Every def system freezes when the trucks not running and it’s cold enough out. Perfectly normal. The truck won’t call for def until everything is up to temperature.

I never run my truck at night since I have an apu and a bunk heater. Even at -15.

 

DEF heater line is bad.

 

Engine coolant heats the DEF tank, electric heat line from the tank out. Warms up enough it will thaw out but should have a code for it.

 

When the temperature gets below 40 is when I start using anti-gel and leaving my trailer brakes released. And I always idle but then again I've never had an APU.

DEF freezes at 12°F, BTW.

 

Always liked to idle 24/7 when it was 10F or colder. Even running anti gel seemed to risky to bet or hope it works. If you gel up you could be sitting for days waiting to get it going again. It has to warm up or you need a tow to heated shop or some has come put blankets and big heater under truck to warm up things up. It seems a lot cheaper to idle instead.

you get -0 or colder even the engine has hard time staying warm at idle.

 

If I remember correctly the company that hired me say never shut engine off at 10f or colder. That was with old diesel fuel. Today diesel fuel gel even more because they took all the stuff out of it. Then add biodiesel to the mix today. You get into the teens temperature it can gel sooner then old diesel.