I tried this feature out about a week ago when it was about 30F, and was amazed that it really works. I was in the store a little over 30 minutes, so it had shut off by time I got back, but the car was still nice and warm. It didn't take but a few seconds after I was on the road again an the heater about drove me out of the car. My God it works, nearly had to roll down the windows to keep from being roasted alive.