This car is supposed to be 1300 cc,but I have Civic Exi 1996 model ( 1500cc) giving me 165 plus on lonroute, with average speed of 120/130,so it mainly depends on the pressure of specific CNg station, which effects our mileage.
Moreover, setting of CNG in Engine, Speed,Usage of gears,displacement of Engine,quality of CNG, condition of tyres,and your driving habbits matter alot.