possum328, easy starting at -30F is a tall order.
You'll probably get good, if not great, service from the Mobil 1 0W-40. However, between now and next oil change, I'd research 0w30 oils to see which has the lowest pour point.
Valvoline MaxLife Next-Gen is a bit of a synthetic blend (some Group V, I believe) with decent cold flow properties. To significantly improve on its performance in punishing cold, you'll want to carefully choose a successor by looking at specs on product data sheets.