Wel friend, saw ur posts in the steer fan club as well...
EXi civic is not focused on fuel average at all... Whereas city idsi is MADE for fuel economy...
In this thread, u can find several posts that depict the fuel average of city if well maintained can easily go above 22 kmpl. Recent posts by Fahad are there...
It would be a wise decision to switch to city any day any time if u want to get good fuel mileage... Even people who were never bothered by civics in the past are now switching to honda city and the new corolla altis just for fuel average...
As for difference between idsi and steermatic, dude, of course idsi is way more fuel efficient. Steer is auto CVT while idsi is availible in manual as well.
Moreover, steer has a 1.5L 16 valve engine. U'll have to hypermile a steermatic for fuel average while an idsi will give u good fuel average even with normal driving....
On the other hand, there are options in steer that u won't be getting in idsi like alloy rims, power, 7 speed mode, paddle shifters, optitron instrument cluster etc etc...
make a thorough study of the recent posts and then let us know if u need any more help...
Regards