depends upon the 1300 cc car u have
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
PS : my car = 2012 Honda City Manual