i have used below mentioned viscosities (from top brands) over extended period of time to reach to my recommendation of 5w-40 or 5w-50.
5W-20 Fully Synthetic
5w-30 Fully Synthetic
5W-40 Fully Synthetic
10W-40 Fully Synthetic
10W-40 Semi Synthetic
20W-50 Semi Synthetic
5W-50 Fully Synthetic
5W-50 is the best combination of protection and performance at the same time. Also gives extended milage advantage so actually reduces maintenance. similar is the case with 5w-40.
Important factor to consider in PK is start stop heavy traffic and scorching summers in cars with bigger air conditioning units which has a toll on engine running temperatures. Add to this our usual habit of flooring the cars whenever we have an option.
so 5w-40 and 5w-50 have higher viscosity index as compared to other oils which ensure better lubrication under hotter/aggressive operating conditions.
So where 5w-30 is recommended on the manual of corolla, i think the manual has not been modified by Indus for Pakistan specially so we should upgrade to 5w-40 or 5w-50 viscosity. Also if we go to any 3s they have by default 2 oils available petron that is 20w-50 and taglon 5w-50 both meant for us specifically.
i hope this clarifies. :).