Hyundai Santro Xing -alto 800 is better than this. Review on Hyundai Santro Xing GL (CNG)

I Bought This Car 4 years ago. Everthing is good but its millage is Very shocking I am getting LPG Millage of just 8-9 km/ltr in city and 10 km/ltr on highway. Where as petrol is approx 12km/ltr. I have complained several times to the dealer but they could not improve it even they dont have any equipment to check the milage/ performence at their service centre every time when I send my car for service. They just wash ad do regular service.well other things are good. The interiors are basic and well suited. The engine is very smooth . You can feel minimum vibrations in the steering wheel at traffic spot. The real beauty though is the gear box with swift and assured shifts which is real pleasure.driving position is ok for short drives, but after some hours you can feel strain due to lack of lumber support and an acute ankle angle on the accelerator pedal.