Mine is an unmodified TH Sports (lowered only) I do all country driving Geelong and back to Meredith etc, only short trips are dropping kids off at school bus.
On average I manage 8.5/100 in granny mode, I use cruise all the time and rarely thrash my car, after all it's not my old 550 hp Mercury Cougar.

It's not unusual to top 900 ks per tank, I made it from the outskirts of Melbourne (where I filled up) and drove to Sydney without re-filling, fuel light had been
on for awhile when I got there, but what the hey it made it