I own a hyundai verna The car give a mileage of 10kmpl in city and 15 kmpl in highways on ac. On non ac the car gives mileage of 12kmpl in city and 18kmpl in highways. I feel that the limeage is very less then comparing other verna. So what could be the problem weather it can be rectified of suggest me a solution.

The person DRIVING the car has a HUGE impact on how much fuel it uses compared to identical cars driven by OTHER drivers. Accelerate fast, slam on brakes to stop rather than coasting up to stop lights or signs, drive erratically, driving fast, carrying a car load of junk everyplace,. among other things will reduce your fuel economy.

Tire choice, tire pressure, driving in a place with a LOT of hills and sharp turns also effects it too... as can a car that simply needs a tune up.

Average is called that for a reason..its an average....many people get better, and many people get worse...this is just the average of what everyone gets. (not exactly true but close enough).

Brakes can drag as well.

If everything else is in order, the best test I know is exhaust gas analysis. If that is out of sorts, the results will guide you to the best repair.