Had to drive to Toowoomba, QLD a week ago.
Filled the tank up there and drove back to the Gold Coast Hinterland. It was a Thursday, mid-day, and traffic was so light that I maintained a steady 100 kph. Interestingly I had to hair touch the throttle, as it wanted to always go to 110 kph. So I had to take my foot OFF the throttle lots. Why stay on 100 kph? That's the max speed in QLD on this route. Even though about 25 kilometres of the M1 are 110 kph, which I did.
Kilometers travelled = 211
Liters of Ultimate used = 12.12
By my calcs, worked out at 50.69 miles per gallon. NICE for a 26 year old.