i achieve that on mixed of city & city highway drive, on eco mode.
mostly weekends go dating or outstation drive.
maybe my driving style is smooth. i dont like sudden heavy braking or sudden acceleration if not needed.
ie, gently cruise to a highway speed & maintain highway speed, or gently cruise to slow down before exit or tolls.

for daily rush hour commute, drive mazda 2 instead.
also able to achieve 800+km on a single 44l tank.

usually, what car manufacturer claims are lab test & not really achievable on real world condition.
i'm pretty surprise that mazda actually delivers on it's FC claim.

but cannot be saud about everyone la.
some drivers heavy footer, prefer the omph of engine rev.
it's ok to not care about FC, especially fuel cheap nowadays.