between UK-gallon and US-gallon there is a factor of 1.2.
So just multiply the milage that the US guys quote with 1.2 then you get the equivalent to using UK-gallons.
Usually I need 13 - 14 litres / 100 km
when in city traffic and down to 11 L/100km cruising at 140 km/h on the autobahn.
Anyone like to translate to the non-metric world.
