Hey GS:
My best advice is to use a 0w-30 or 5w-30
synthetic.
I live in Connecticut and before I start ol' SPF642 in the winter I put a 60W light bulb under the crankcase the day before to help warm the
oil. I put a piece of foam rubber in front of the
oil cooler and I cover the bottom half of the radiator with foam so that the water entering the block is a little warmer than ambient.
Bob