Cars Q&A

I have a accent petrol 2005 model. the problem is that I am getting very low mileage of 5kmlitre of petrol in city with AC on. I heard that accent petrol usually give around 11-12kmslitre in city with AC. I got it checked at more then 5 mechanic and they say everything is fine. What needs to be checked for faults for getting low mileageAny suggestions me . what can be done to improve the mileage Any petrol additives etc Please suggest.