Originally Posted By: oil_film_movies
For the extreme cold in the winter, you could use any 0w40 you see (all brands are good in the 0w40 arena). Plus, when you change the oil with the thick (hot) 0w40, leave it a half-quart low on purpose, like half-way between the Add and Full lines, and put in a pint (half-liter) of Kreen, Seafoam, or Gumout Multi-System in the oil to assist in the extreme cold startups. It will gradually burn off, as designed, and will temporarily get you through the cold months as you add it. (Then stop putting it in when the temperatures gets above about -15 degC or so when its not needed.) Never over-fill, but you can keep the level at the full line during the cold months using the thinner fluids.
I wouldn't use any oil additive for a newer car that is still under warranty. Any 0w oil will be fine without thinning it out more with other additives. If a 0w cant keep up (it can) then plug in the block heater.
And yes OP, 0w40 is perfectly fine to run year round in most climates.