I live in Minnesota, plane lives in an unheated T-hangar…the winters do tend toward the cold side. I can’t heat the uninsulated hangar…if I do, the snow on the roof melts, drips down, and freezes the hangar door shut.
So I don’t worry about keeping the airplane warm, although I do have a little ceramic heater I keep in the cockpit that I can turn on remotely with my phone. The engine has a Reiff Turbo XP sump and cylinder heater, also on the cellphone switch. If I’m flying later, I turn those two heaters on 4 hours or more ahead of time. When it’s time to fly, the cockpit is toasty warm and the engine oil temp is at 70-100 degrees. I’m no A&P, but I’m told that starting a cold airplane engine is very hard on it.
Unrelated, but the first thing I do when putting the plane away after a flight is hook it up to a dehydrator and purge the crankcase of the moisture associated with an IC engine and which will condense as the engine cools back to ambient.