Low oil pressure

IMO, one thing that is helping you use 20W50 year round is your location in southern CA, near San Diego. So your good experience is for a warm climate and is likely not as applicable to cold climate use of 20W50. Redline recommends not using their 20W50 at low temps at around -5F and below.

All true. I did have my Charger in Indiana a few years ago, yes I drove it there. It did get cold, snowing and Ice, and I kept the 20/50 oil in it. If I was to stay there, I would have switched it out. I did not drive it much in the snow, I was worried about the salt and rust.