I never bothered with synthetic in the Civic - just regular dino changed religiously at 6,000 km intervals. So far, so good - and that's after eight years and 250,000 kms, a fair bit of which were done at 8,000 RPMs on the track.
What I have done the past couple of winters, though, is switch to a semi-synthetic "winter blend" for the colder months. Much easier starting when cold, much cheaper than full synthetic, and so far no problems in switching back and forth with dino oil in the summer.
One other thing, BTW: "wind chill" is totally meaningless as far as your car is concerned. To an inert lump of steel, minus forty is minus forty, no matter how hard (or not) the wind may be blowing.