my mates vy ss is a manual and he drives pretty conservtly and the best hes had with frway and city driving is 17.5! he once picked me up and was on empty so went to servo he put 30 buks in and from liverpl to bankstown and back he had to put another twenty in,this was around the same time i was getting ready myself to buy a new car and it really put me off hence the v6
obviously i now know they vary massively and ive regrettd it ever since.shouldve listend to the dealer wen he said ther only 2-3ltrs diff.