An original 1972 4/4 will just do 40mpg if you keep it below 50 and drive smoothly. I got around 30mgp normally and when I fitted a tuned engine it dropped to 25 even if one utterly behaved.
Competitive mpg though was less than 10. I ran it with about 2 gallons in the tank and frequently had to add the contents of a one gallon can to make it through the day. Event mileage on hillclimbs was often less than 8...
