mate driving on highways requre less braking thus the fuel economy on highways is better and mantaining a speed below 100km improves it further..
in city driving it is a different story, you have to accelerate at times, frequent braking, idling at signals which means more fuel burnt.
on highways my car does about 15kmpl and I believe it can do better on highways with speed less than 100km/h but in city driving its a big NO!
Sidenote: damn I feel like an idiot, bashing the car that I own.
to my honda: cheer up, atleast Im not being biased, I still love you baby.:*