The Normal Working Temperature of Engine Oil in car is typically 75 Celsius to 95 Celsius after which thermostat opens to cool down.
A general trend among people here is that 0W-40 is thinner oil which gives better fuel mileage and is better than 5W-40 which is better than 10W-40.
Looking at Product Specifications, following is Kinematic Viscosity of ZIC engine oils at 100 Celcius.
0W-40 = 14.35
5W-40 = 14.4
10W-40 = 14.1
We can see here that Kinematic viscosity of all Engine Oil Grades is almost same at normal working temperature of Engine. So, there is no thin or thick oil at normal working temperature, its only at the cold start when oil is thick or thin.
So, my question is "Aren't we buying premium and more expensive Engine Oil in Hot Pakistan Temperature for no reason at all with not much gains".
Also, "Isn't it better to put 10W-40 engine oil and change is every 3k kilometers and more frequently than to put 0W-40 engine oil and change it after 10k kilometers which in some cases takes 7-8 months".