[throwaway672000]

I don't think I would see anything wrong with gallons per 100 miles if I was used to it. Especially if it was "gallons per megamile" or whatever.

You see (at least in the UK) dishwashers say they only use x litres of water per wash or even things like "this only costs 10p an hour running costs".

It feels like one less step to get to "how much would this car cost me for my 250 miles a week" - which seems more common than "I can afford exactly 2 gallons of petrol a week, how far can I get with this car".

Maybe I'd feel differently if we bought fuel in the same units we measured its consumption in!

[ingas]

I don't see anything wrong in measuring gallons per mile and measuring in yards and other non-metric systems when it's something local. Maybe it's convinient if you live somewhere where everybody accustomed to that.

It's when I see articles about space exploration with miles and pounds - it feels wrong.