Brother, the mileage also gets affected by the tires you use and the condition of your engine, plugs, air filter etc and also how much running have you done on the engine. My Santro exec 2005 have done 100k kms and it's giving me 10-11km/ltr in city with AC full on. My compressor is weak and it puts a lot of load on the engine. So in order to get perfect mileage, your car must be in perfect condition.