I run 20W-50 year round in my MG, although admittedly my winter driving is limited.
Even so, I've started it down around 10ºF without any special tricks. I just give it full choke and wait for the floats to fill. After that, the first crank or two will sound fairly anemic but it picks up and usually will fire(and stay running) after the engine has turned over 3-4 times. If the car had an accelerator pump so that I could prime it, I'd probably get it to fire on the first or second revolution. Also, once the oil pressure is up I start reducing the choke, and even stone cold it will stay running with 3/4 choke or so. On cold days, I usually keep it at 1/3 or 1/4 choke until it's most of the way warm, but that's mostly for better throttle response(i.e so I'm not struggling to get it up to 2500rpms when pulling out in traffic).
On the other hand, I also run Mobil 1 5W-20 in my Lincoln, and it starts pretty much the same in sub-zero temperatures to up over 100º. It might be a bit reluctant on cold days if it has sat for a few days but otherwise will start either as soon as I touch the key or within one revolution.
