20,F or colder is my plug in number, my
L3400 starts easy at 0-10 degrees F. when I plug the block heater in for just 1 hr., IF I was in a hurry.
On a Saturday morning I get up at the crack of 8:30, put my slippers on, look at the temp. 8,F, get the stove roaring, plug the tractor in, (not far from house) if it's 0 or colder I run back inside, make coffee, have some Grape Nuts, drink coffee, check TractorByNet, 6 cups later it's now11:30, where the time go?, check temp, 15,F, Oh boy heat wave, start tractor with 10 count on glow plugs, starts like July, get my chainsaw and put in an exhausting 4 hr. day!
I guess the moral of the story is, I don't like starting a cold engine with Rottela 15W40 motor oil in it, seams to me that creates a lot of engine ware, and I was told once that the first min. is the hardest on a motor.