Rotela is nice, functions well for climates with mild winters. If temps get really cold, a zero weight is preferred. Mobil 1 is thin but their 0w40 will still give you a thick 30 and excellent cold operation. Amsoil SSO 0w30 is the best cold weather 30 only bested by some 0w20s. Eneos makes a 0w50 that works very well in winter if you need a thick oil with great winter performance. I recently went to Motul 8100 0w40 to try out, but coldest so far is only 30°F.