Originally Posted by kerry

When it's below about 10 degrees and I have to drive early in the morning, I'll typically start the TD when I get up and let it idle for about 45 minutes before driving it. It melts the ice of the windows and warms up the interior. I can't recall what the temp gauge reads after that amount of idling but the temperature is high enough to get the interior toasty. That's probably only a dozen days a year so I'm not about change my behavior and start scraping icy windows instead.
By the way, it is illegal to do this in Denver. It's called 'puffing'. I use two keys and always lock the car when it's running.