As per feedback from Careem drivers in Karachi, it never gives more than 12 km per litre no matter how carefully you drive it. All cars had stock tyre on them.
One driver even claimed than the there is Throttle sensor issues in some new wagon R due to which those models never give more than 12 kml. the ones without any throttle sensor issue give upto 14kml in city. Maybe wagon R owners can share their mileage in city.
However this is a bit hard for me to believe. maybe an expert can add to this.