I just did some testing/calculation with XRT. Gear ratios were normal (like you would encounter in real life) 5th. 100kmh-2500rpm, 200kmh-5000rpm
First I took it around KY oval. Did 5 laps around it at
90-100kmh. I got
~4l/100km ,MPG: 70(UK/Canada), 59(US)
Then On KY oval again, but at
200kmh constantly (more throttle on the slopes, less on downhill).
~15.5l/100km, MPG: 18.2(UK/Canada), 15.2(US)
And finally, whipping the car around Fern Bay Black (
2 laps full throttle, including few burnouts).
~29l/100km, MPG 9.7(UK/Canada), 8.1 (US)
PS: I used this to convert the units into gallons
http://www.euronet.nl/users/grantm/frans/fuel.html
There was a chart/pic long time ago where there were most of the cars fuel consumptions. I tried to find it but i failed
PS2: This info might not be 100% correct