When did you last put a gallon of petrol in your car? Or measure your journey by road in kilometres? If we are really never going to finish the job of going metric why not express fuel consumption in miles per litre or litres per 100 miles?
Coming from a country that uses litres/100 km it is very odd and difficult to get into the imperial system. The funny thing is that UK is all alone on this one. America uses miles too, but at least they have the decency to have petrol stations with GALLONS.