Just before sundown on Christmas even I feed the birds just outside the garage and when I came back in I hit the down on the remote and stuck it in my pocket and somehow accidently pushed the button again stopping the door from closing any further. About 9:30 Christmas morning I went into garage to put trash in trash cans and discovered dooor open (about 2 ft) and the digital clock & thermometer reading 17* F in the garage and -3* outside.
I have an insulated garage with a small oilfiled electric space heater to heat it in the winter and it was on at the low setting is probably only reason it wasn't colder in the garage.
Now for the funny part, the first thing I thought was
will the MB start? We leave the keys in the cars, so I just opened the door of the 240D and leaned in turned the key to start and waited for glow plug light to go off then hit the starter. The car started on first compression stroke, and sounded like the verry devil running. Once oil pressure came up to max and it ran for a minute it started to settle down to normal noisy self.
Now this car has no block heater, but is running on 49 cetane B2 fuel. I think the high cetane fuel is the reason the car started so easy, that and having rebuilt the starter last spring. I guess a well charged battery helped also. I didn't check wife's car, because I've seen it start after sitting out in below -5 below zero weather without hesitation.