I live in the north and see winter's cold. I drive a 87 300DT currently less than a year. Last car was a 84 300D and never spent a winter's night unplugged, otherwise you could forget about starting it!

I never took a temperature reading while plugged in and wonder how high the temp gets in the block overnight. Warmth must be good for the engine, as ice cold engines at start-up must wear a lot more!