How come no-one has mentioned using block heaters, oil pan heater and battery heater/charger? I live in alaska, where the temperatures drops to -45 for months at a time... Needless to say, all our vehicles on the road are "winterized".
Put a block heater in, and silicone a 100-150 watt heat pad to the lower part of the oil pan, and install a battery wrap blanket, or a 12v trickle charger/maintainer for the battery. The block heater will keep your block and coolant warm, the oil pan heater will keep your oil viscous, and the battery blanket or charger will keep your battery charged and keep from freezing. You can also silicone a heat pad to the tranny pan too, although that is usualy optional.. Connect all these with a 3 or 4 way box plug, and plug it in for 2-3 hours before you need to start.. You will have no worries then.
Oh, and use 5w-30.

Block heater $25
150 watt silicone pad $20
battery blanket or charger $20
3 or 4 way box $15

 

Solid advice. Everyone around here was freaking out about their vehicles because the forcasted low was a deathly 29* last night[8D]

 

I dont even think twice about my vehicles until its below 0 degrees... just run 5w30 and let it warm up a bit before you race off and you will be fine... 29* is a heat wave for us! I suppose if you had 20w40 oil and 80w90 gear oil and 100% glycol for coolant, your car might be slower to start and move.. but still, nothing to really worry about at 20 deg..