[astolarz]

To me, this is the best argument for l/100km (or gal/100mi). I don't know of anyone who really thinks about how far they can go before they have to refuel. They just check the gas gauge and fill up when it's low. There's very few places, even in the US, without a nearby gas station so it's not really much of an issue. The arguments about multiplication vs. division also seem silly, especially since your math teacher lied about not always having a calculator.

That said, as an American I grew up with MPG so that's what's intuitive to me and I'm happy with it. Something like l/100km seems like it would be mostly useful when shopping for a car than actually getting around.