Just did a round trip from Sydney>Coffs>Brisbane>Sydney with minimal round town use of the car during the trip
2011 SV6 3.6 auto sedan, 11,000k on the clock, two oil changes so far and has Castrol Edge 5w-30 in it.
Trip up, me only with minimal luggage, trip back, me only but around 200kgs of luggage between the back seat and boot.
Just shy of 2000kms all up, average speed 102kph, a/c on for approx 70% of the trip and cruise control for 95%.
The car averaged 8.18 litres/100 km (not from the dash display but real life fill up figures).
Pretty damn impressive I thought but I did baby it for most of the trip