The first thing I noticed in my Metro is that even though it was 4F outside, the engine fired right up at the touch of a key.
It warmed up pretty quickly and I hit the road.
That said, once I got up in the mountains I parked it for about 20 mins, and the temp gauge was already almost all the way down. That was quick even in this weather. I had just driven for an hour and a half at WOT.
There's comparatively little mass in the 3 cyl engine, and no insulation, so I don't see an easy way of storing the heat in there for any length of time.