Nano BS3 and BS4 difference

BS = Bharat Stage. These are the pollution norms that set the maximum permissible limits for the pollutants emitted by an automobile that is to be sold in India. Each successive BS norm is more stringent than it's preceding one. Right now we have BS4 norm in place. The preceding one was BS3. A car that meets BS4 norms would pollute the environment lesser than a BS3 car. Apart from this fact, there is no difference. No difference in power/mileage. No problem if you go for BS3.

Thanks a lot Sam. Very clear answer. I decided to go for Nano BS3 since i am tight on my budget.

I think that the Tata has address the Noise issue in BS4, There is a difference in air filter and the converter, opting for BS4 would be good, but if you are tight at budget go for BS3, I have driven many petrol cars for a long time, but when you take this beauty uphills this little baby performs really well, it happens due to the engine on the back and center of gravity. I have booked the car as I had Maruti 2000 5 speed model but I like Nano More due to headroom and the performance during the AC is on.