I drove 60 miles to a neigboring city last week at 5:30AM and it was 35 below zero. The Dakota wouldn't shift into OD at that temperature. Usually have the block heater plugged in at anything much below 0. It has been well below 0 most of the last 3 weeks and the vehicles go every day. The wife's van doesn't have a block heater and it starts and she goes to work every day.
don't even think about starting one with 20/50 oil in it, I don't even like to think of that at 35 degrees. That stuff gets real thick in hurry. 10-30 is bad enough.