Newer models are generally designed for better fuel economy. I agree that most of the people exaggerate its mileage like it does 17-18 in city etc. But honestly this figure seems un-realistic or super ideal.
A very healthy good condition new model Mehran gives like 14-16 max.
But if you drive on motorway constantly at the speed of 60-65 km/h, then yes its possible that it give 18-20 km/l average.