They are fairly accurate; you might as well say that the speedometer doesn't show correct speed and is useless for determining speed.
Pump readings aren't wholly accurate either; a slow fill actually gives you more petrol than a fast fill, where there is evaporation loss (most petrol pumps fill at the maximum possible speed).
Btw, my Civic Prosmatec usually manages 450-470 km per tank with A/C in mixed driving. Its usually driven by my dad. I explained 3 stage VTEC to him, torque converter lockup, and the minimum shift points of the transmission (1-2 shift at 10 km/h, 2-3 at 32 km/h, 3-4 at 50 km/h). Just by following these guidelines, as well as staying in the 60-80 km/h speed limit, he manages 12-13 km/l.
The same car, when driven by me, managed a 56 km highway trip at 21 km/l (I know advanced hypermiling.)
Are you aware exactly how i-VTEC works? How can you manipulate it to give you more mileage?
