Mine is a LE CNG. Within city it is something like 1.65Rs /km and on highway it is 1.30Rs/km (thats without AC)
Petrol: within city it is 13-14km/l and on highway it is around 18-19. I have even done around 23km/l on Motorway but driving around 85km/h speed.
But guess Karachi is a city with alot more traffic...and am not sure about the quality of gas there...these two factors are the most important.