First of all a very few car company model gives a factory fitted CNG.
In India if the car is equipped with factory fitted CNG then it means that it is targeted for the buyer who are looking for a CAR which runs at a cost effective price and with some good or average features. [normally these audience do not buy a car costing above 5 lakhs]
Since CNG is not available in every part of the country as like Petrol or Diesel, so this might be also another reason, I guess.
To answer your question,
- MS Wagon R [that too Lxi model only]
- HM Ambassador
- MS Ecco
- TM Indica eCab
I think only Maruti provides their CNG kit without voiding the warranty for any car. You need to check with MS dealer. Getting CNG kit fitted outside the showroom will hamper the warranty of a CAR.
If you are spending 8 lakhs on a CNG, I would rather suggest a Diesel variant in hatch or sedan.
You can get a good Diesel car with bigger boot at that price.
for an example:
- MS Swift Dzire
- Honda Amaze
- Hyundai Xcent [launching very soon. Booking has opened]
- TM Indigo eCS
- TM Zest [launching this year end, wait till Diwali. Tata feels this car to be promising]
Or you can buy a 3+ year old petrol car, and get CNG kit fitted from market. There are lot of shop who does this job. Some kits available in market,
Some knowledge article to types of CNG kit, CNG Kits and their Types | Features | CarDekho.com