If I recall, the average consumption of petrol was approx. 8 miles to the gallon. You metric buggers figure that out for yourself....I refuse to change! So it depends on a number of things, but we need not get into details. As Terry says, keep an extra Jerry Can of Premium in the back....or if you get a chance to stop along the way...just top up. You'll get the hang of it and you will get some idea of how much petrol your going through.
AND as for the Unwashed Ford Heathens of Shilo Manitoba....spare the tow rope.

Robert