On my 05 I can have good heat within about 8 miles, provided I keep the RPM's up to around 2000-2400RPM's, even the couple days we had here that it was below zero. I tend to let it idle for about a minute after starting in such temps (unplugged) and then drive it somewhat gently until it's off the 140 mark. Starts to get warm enough to defrost the windows after just a couple minutes of driving.