When running-in a new pair of Distanzias in the UK I got 79mpg
report which would equate to 174 miles to 'reserve' and 261 miles per tank.
My latest mileage check in Spain was 105 kilometers (65 miles) to reserve on a Sirac front and a Karoo rear mostly off-road or 31 mpg (93 miles per tank).
The tyres you use and the type of road/off road has a huge effect on mileage. Admittedly that was on two different XT660R bikes but they are both modded similarly - PCIII (CaptMoto II UK - rich Zambesi Spain), snorkel,Kev's airbox and re-breather, K&N, DNAII, the only other difference being CCC longs on the UK bike and CCC stubbies on the Spanish one.
The UK bike is set up for general mainly road use and the Spanish one for maximum torque for hill climbing.
Those figures are both probably extremes which will not be achieved in normal running on a bike with part-worn tyres, but the Distanzia results were most encouraging for twisty road use and I am looking forward to returning to the UK mid-June to see what the results will be when I can really wind them up.