I never really cared about the oil filter bypass valve and thought it would only open if the filter really gets clogged up but recently read a few things about it opening on cold starts and when taking off with a cold engine when the oil is really thick and this sounds scary to me. Maybe i'm overthinking it, especially if owner's manual chart says 5w30/40 is ok down to -30c, 10w40 down to -20c and 15w40 down to -15c and says not to warm up the engine before driving. I let engines idle for at least 30 seconds up to a minute before taking off and try to shift at 2000 rpm max until coolant temp gauge starts to rise above 40c. I use 5w40 or 10w40 and temps are almost never below freezing. Could it justify 5w40 over 10w40 at freezing as well as short OCI to keep the oil really clean and reducing cold start/driving wear in the long run?