Hi Nasar, Nissan Micra is expected to be launched with both petrol and diesel engine options - the 1.2L, 1198cc petrol engine will deliver mileage around 12.5kmpl in city while on highway it will offer 17.2kmpl.. while the diesel variant will be powered by the 1.5L, 1486cc diesel engine that offers mileage around 13.6kmpl in city while on highway it delivers 18.2kmpl ..
We encounter similar question many times, the easiest way to increase the mileage is to keep your car healthy. Keep the tyre pressure proper, air filter clean, always follow speed limits and turn off your engine on traffic lights. Find more tricks here- Please find the details Chevrolet service centers here- http://forum.cardekho.com/topic/356-how-to-increase-mileage-of-your-car-tips/
There is not any special petrol recommended for NIssan Micra. You can use simple unleaded petrol in it. However, you can use Speed, Power or Extra premium petrol for better performance of the vehicle.