What engine oil are you using? Use any good 05w-30 grade.
Where do you live? If in Lahore, take it to magic motors in Model town near "Goga naan chanay". They charge very reasonable and have got all the tools and that computer scanner thing too.
What is the top speed you are achieving?
There could be many things affecting your fuel consumption.
When was the last time you got your throttle body cleaned?
Have you ever used high octane?
Ever cleaned or replaced spark plugs?
There are many sensors in this cars and some of them needs cleaning. Have you done that?
Last but not least get your catalytic converter checked. Mechanic can see it by opening the silencer and check visually if it looks clogged.
Maybe its time to get your catalytic converter removed or replaced(costs 42000).