verslagen1 wrote on 12/01/12 at 11:17:07:5 minutes is not an issue, 30 would be.
and it's richer throughout the range.
But what if you lived in Alaska, and had an hour long work commute at -40F, would it then be permissible to leave the choke out?
I had a friend who used to be a farmer in Wisconsin. He told me that they drained the coolant in the tractors during the winter because it was so cold the motors ran fine without it. In other words, there was enough surface area on the head, block, and oil pan to dissipate the heat, plus it avoided freezing problems (popping freeze plugs, etc.).