once engine is running, its the same temperature whether its winter of summer.
secondly, if you engine doesn't reduces oil, its better to put the most thinner oil that you possibly can get. It makes engine happy and effortlessly running.
That's what I have experienced.
well if you let your car parked for several days then the first crack in critical. but if you start it daily then these oils are not thin as water. so doesn't make much different.
