Tata claims that Nano returns a mileage of 25.4 kmpl. Fuel economy depends on various factors like driving style, traffic conditions, road, etc. however, the Nano returns a mileage of around 18-19 kmpl in city and 24kmpl on highways.
New Tata Nano with EasyShift is available at Rs. 2 lac (Ex-showroom, Delhi), and the final cost depends on the valuation of your car. So, first get the valuation of your car from authorized Tata dealer, so he can give you a final quote for the new car.