Johan
Ex got M3 in the divorce, waiting for EU Model Y!
L/100km is likely used so that you aren't having to use leading zeroes, as you would with L/km.
l/100km is used in European countries, because they're rational, and figure that a measure of consumption is better for comparison than a measure of range.
This. It's a frame of mind thing.
Historically it reflects the US thinking v.s. European thinking. My guess is in the US gasoline has always been relatively cheap and "fuel economy" has mostly been about just that: economy (as in financials) i.e. how much is filling this car going to cost me. While in Europe we have been used to thinking about consumption from not only a purely financial standpoint but also with regards to exhaust/pollution/environment etc. In this case consumption per distance travelled makes more sense to use than distance travelled per unit of fuel.