Hi there - My 2 cents worth. I vary between using 0w-20 & 5w-20 and so far the best mileage I've gotten within Lahore is 28 km/pl, with minimal AC use (previously the best I could get was 26 km/pl). With regular AC usage, its hovers around 23-24.
For the tires I go down to a lower PSI of 32 in summers and keep it at around 34 in winters.
The only time it was driven on a long route was more than a year ago to Nathia Gali and back, the mileage then was 22.5 km/pl driving between 100-110kmh.