You will (should) be able to get by with an oil pan heater and synthetic oil, that was always enough to get my car started at 10 below. I could get it started, but it was tough at that temp - lots of cranking and lots of smoke.
A block heater is much better. Just glow the plugs and fire it right up. I don't think a garage will help much for overnight when it is cold.

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andy t
'78 300d
'95 volvo 850, wagon
'86 300sdl - engine out, maybe I'll have it rolling by June

whole bunch o' bicycles