I know it's a pain, but put the frost plug block heater in. You'll be glad you did.
0W40 oil is a big help too. I know it's expensive, but I've got it in both my idi cars for the winter. Block heater quit in one of them and I haven't had a no start yet.
10X on that! We used to use a replacement center pan, with heater, on the air cooled VW's (about 100W) and they were better than nothing, but not much. My old Volvo 544 however, had a 200w heater, in place of the block drain tap at the back of the block, and it started consistantly, morning after morning, at -40. It did start a little odd though, as the heater only got the rear carb warm enough to flow gas. So, it would start to fire on cyls 3-4, slowly building speed until it disengaged the starter and after about 30 sec, 1-2 would kick in. But it
never failed to start Here's a strange one for ya. Dodge/Cummins trucks, in the USA, come with the block heater installed, but no cord. The cord is part of a 'Cold Weather Package' (cord and a winter front) that is a $90 option. In Canada there is no 'Cold....Pkg' and the cord is installed from factory. BTW, they take a different cord than most others, except Ford diesel. They have a threaded retaining ring so they don't shake loose.