I was in some pretty cold weather with my 08 Duramax. It started great, remote start , or key. The only thing it did differently was as you start driving, the glow plugs cycle and the draw makes your headlights go dim. I was staying in a camp up in northern BC, Canada and I had a 10 mile drive to the worksite and most of the way to work I had the headlights dim for maybe 15 seconds or so, then go back bright. That truck had the dual alternator option so the glowplugs draw a lot of juice. I actually thought I had an electrical problem, then talked to a few guys that lived up there and they told me it was normal for a diesel to do that in real cold weather. The truck was around 3 years old at the time, I kept it for another 5 years, that truck was flawless for the 8 years I had it. Sure hope my new beast is as good.