i idel below 20 i can't sleep colder than that and above 65, when i had a bunk heater in the truck i would only idel below 0 never had a problem with fuel gel..
if i am cold I idle for heat if i am hot i idel for the ac just that simple ...boss is home and cozy so I will be too
In this temperatures you should idle AND add additive. A good idea to ask you co to check batteries before the season,if the engine is cold you might get only one chance to get it running or you will have problems with the dying battery.
I use to never idle the truck in the winter unless it was severe severe severe.. now I will idle at about 35 degrees.. If i start to get cold I idle. I got pretty sick one time trying to save a mega carrier money and soon realized when you are sick they still want the load there on time and they don't care if you were trying to save them money or not.. On the other note don't idle when you go into eat get fuel are just setting around waiting.. In other words try to save the company money if you can this is where your raises come from but also don't kill yourself trying to keep your idle % down.. I would really be idling at 19 degrees.
I only idle when I need to be comfortable. If you purchase fuel in the region you are running then it should be treated for the weather. I keep a bottle of alcohol with the highest alcohol content in case I get water in the fuel or it starts to gel. It has prevented my fuel from gelling on more than one occasion. I also use the alcohol to pour in my air lines in case my brakes freeze up.