20w50 seems pretty thick to me. You’ll have a tough time starting in the winter I would suspect.
I generally run 5w40. I’d be down for 5w50, but that’s not readily available at most auto parts stores in my experience.
5w50 mobil one is A40 Porsche spec. I run it in my GT3. It’s easy to get through Napa etc, only issue is that it’s not available (or I have not seen it) in jugs. 15w50 I use in my air cooled Porsche. It’s cheap in jugs.I generally run 5w40. I’d be down for 5w50, but that’s not readily available at most auto parts stores in my experience.