I've done quite a few drives between Brisbane and Gladstone (550Km) and I have found that driving in "S" Mode is more fuel economic than "D". I've had the car down to around 7.6L/100 driving in D and 7.2L/100 Driving in S. Both times there was roughly the same weight in the car and same time of day. Could this be helped by dropping it down 2 gears or so before a hill or mountain, as apposed to letting the car change down when it can't quite keep the pace up?