I have been driving a 96 Civic Exi for more than 10 years now. First of all, don't believe the meter. Any car from 1996-98 will have 250,000 or more kms on it. If someone tells you they have a rare low mileage beauty, they are probably lying. My car has done more than 275,000 on the original engine, never driven on CNG.
Although I don't recommend buying such an old car, but on the plus side, this model is an absolute joy to drive. If you buy from a dealer you will most probably have to spend a lot of money on suspension and repairs. Buy from individual seller. As for fuel consumption my Exi can do 10-11km per liter with ac. without ac it can go to as much as 12-13km/lit. On the highway you can get 15km/lit and even 17km/lit if car is not completely loaded.
Any question you have about repair and maintenance you can ask me.