My Mercs are parked in a garage, but I still like to at least plug the 617engines in if the temperature is below 35F. The only 'draw back' to doing this is that a weak battery could be hiding. Allow me to explain. I have been driving my 1981 300D daily for a while as the 1985 is getting repainted. My 1981 always starts quick in the morning at home and when I leave work in the late afternoon. A week ago I traded my car for a friends truck to tow my parts car home that I had purchased. The next morning I took the truck back and went to leave in my car. My friend does not have a garage so that car was outside. That morning was in the high teens and windy. I cycled the glow plugs and turned the keys. The engine did not start immediately, but I held on cranking for a few seconds excepting it to start. Well, suddenly I went from what seemed to be full cracking speed dropped down to barely turning the engine. All is OK now, but it is time to replace that battery. By the way...trying to jump start a diesel from a small non-diesel battery is a joke. My friend had a large engine starter. That took care of getting started in a flash. I am getting me one of those.

My S-10 came with a factory block heater. I plug it in during the winter as well just because I can and it allows for quicker warm up. I have also installed heaters in other gassers that I have had. If the temperature gets below 10F an engine block heater is a nice thing o have, especially if you vehicle is parked outside.