Hahaha toyota uses 20w50 in a lot of cars and they do just fine
I just described from temperature rating.
Thing is using less winter grade 5w or 0w helps in cold start of the engine which is inturn good for the engine life. In murree etc in winters the temperature easily goes down to -10 degrees. At that time the 5w grade will perform better than 20w grade which you have mentioned.
That is why 5w is enough lowest winter grade you wanna go. 0w is an overkill.
Most of people using 0w-20. I dont have the problem with winter grade 0w , i am concerned about the summer grade which is 20 which is way less if person is operating his car in outside temperature of 40 degrees. So atleast summer grade should be 30.
If he chooses 0w30 its a good choice. 5w30 is a good choice. But 0w20 or 5w20 is not a good choice for summers and hot weather.
Toyota has also introduced taglon 5w50 for pakistani weather which is good for all over pakistan. But it decreases the fuel efficiency too much.
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