mbz,
I just replaced the GP on my car.. Unfortunately this is my daily driver, it's been in the 30-40 range at night. I have plugged in the block heater, then letting it crank for 30-60 seconds would start it up...
Coming home was a little harder, ambient temp of 50-60, cranking for 1-2minutes would start it up.
I was in a pinch the other evening to get home when I thought to try this.. After a bit here I found someone else mentioning doing it.
My thought process: compression heats the fuel, it must heat the cylinder.. Eventually it will heat it enough to auto-ignite. This will work if your in a pinch.
Also after your car's engine is warm, you don't even need to run the GP's
Hope this helps