Never buy a CNG vehicle. You will commit the greatest blunder. In Hyderabad there are only 8 to 10 CNG gas filling station and one has to wait on the main road from minimum3 hours to 6 hours to get a refill. Start and stop your vehicle at least 100 times for that kind of waiting.
The gas stations are all cheats .Your cylinder of 10 Kg will hold only maximum 7 Kg because rest all they fill with air and it covers barely 110 KMs. It is a nightmare to have CND vehicle. For long run you are gone .You will find gas station in a span of 400 KMs only in highways.