I have tried various oil viscocities like 0w-20, 0w-40, the car ran very nice on them, but fuel economy dropped by 2-3 kms. I switched back again to Taglon 5w-50 and fuel economy suddenly came to 12 from 10-11 kms in city drive.
Some friends are using 5w-50 from day one and have driven their cars more than 100,000 kms without any issue and engine is still as good as it was on day one.