Getting off topic but I just did my calculations.
MFD says:
689km
20km left
ave speed 77kph
time 9hr 37 min
consumption 7.4l/100km.

Calculation
Trip metre 789.7
fuel 52.34l
consumption 7.59l/100km

Car is 2007 RS with 44827km using 98octane fuel. Most of this was country driving although some was slower due to my wife who was following be being unable to go through a bend without slowing down so even though I was in a 100 zone, I had to slow to 70 or so for her to catch up. I will educate her later. I possibly filled the tank more this time than last time so it might be a little out.