I have a city 98. It has done almost 230,000 KMs... so far so good. I converted it to CNG in February this year. It has done 18,000 KM more since then without any problems. I think you should start on Petrol if possible though I often forget to do that myself.
Anyways the car has not given me any major problem so far. Just keep servicing it and always use genuine parts if you have to replace anything.