In twin cities, it used to give me 12.5-13.5 kmpl on my route (from home to office and back) and driving conditions. I always drive with soft pedal and with utmost care (and now, on highways too).
On LHR-ISB motorway, I used to get the same mileage as my speed used to be 140 kmph (and above
), and once I drove around 85-90 kmph and it gave me around 20 kmpl + fuel efficiency.
If you will drive it around 110-115 kmph on highways, I am hopeful you will be able to get around ~16 kmpl fuel efficiency easily.