Wa Alaikum Salam. If car is behaving absolutely fine, then no need to do any sort of chaaeer chaar. Just keep on using 20w-50.
Else if, nearest safe bet can be 10w-40 (preferable) or 10w-30, but try / switch at your own risk.
And 0w, even 5w series oils may be sincerely avoided. I am not recommending them in your particular case.