yes, it's possible for a vios (auto) to hit 600km with full
tank.
i was driving my brother's vios (manual though) from sg to melaka
(during deeparaya festive) and back without needing to stop to top
up fuel. before i started off from sg (woodlands), the fuel guage
was showing 3/4 tank and trip A showed about 210km travelled (he
always reset trip A to zero after filling full tank)... so i didn't
bother to top up and went straight to melaka.
the distance from JB custom to melaka (alor gajah to be exact) is
around 220km... on my way back, the last fuel indicator 'bar'
starts to blink (meaning it's time to top up) when i reached the
last toll (skudai toll) of the north south highway... and i saw
trip A showed around 650km... so, with the last bar left, i could
still push till 700km but what for, right?
so, to conclude, a vios manual/auto can clock up to 600km or more
per 45 litre of fuel (based on an average footer driving habit)...
so there!