if u travel @120 km/hr constant on Motorway, car would give u around 17 km/liter
if u travel @100 km/hr constant on GT road, car would give u around 19-20 km/liter
above 2 readings are tested and tried readings on my car multiple times. also depends upon the way u accelerate to get these speeds. i mean u can touch 100 or 120 within 15 seconds, and also within 1 minute..the base line is if u keep the revs low in every gear, u wud get a good fuel average.
i, personally, always prefer GT road. its short in distance, not boring and u dont feel sleepy on it
Your liana will give somewhere around 16-18km/lt if driven around 110-120 km/hr mark. So you will consume 20-25 ltrs of petrol.
I prefer m-2 because there I put the car in 5 th gear and dont change the gear until salt range than after salt range again 5th gear. It takes around 3.5 hours drive with a stop over and you will fresh while on gt road there are atleast 10 toll plazas and you have to reduce speed on every city. In my case Gt road journey always took 5 hrs and m-2 only 3.5, so I prefer m-2