[midasuni]

Miles per litre would be fine, even km per litre, but the metric way of measuring flips it over so bigger is worse rather than better, so it doesn’t catch on

The numbers don’t work out too, “litres per 100km”. Why not millilitres per km (or litres per gigametre)

I drive X miles (or X km), I then fill up with Y litres (or Y gallons)

If I put 40 litres in my car and do 16 km per litre that’s 640km of range, simple calculation of 40x16

If I need to travel 260km at 20km/litre I need to but 260/20 litres or about 13 litres.

If I put 40 litres in my 3.6 litre per 100 km my range is 40/3.6 = 11 x 100 = 1100km.

If I need to do 260km at 3.6l/100km I need to do 260/100 = 2.6, times 3.6 = 9 litres.

With the “metric” way you need to do two calculations.

if you insist on using volume per length, I’d personally prefer 36ml/km, then I know I need 36x260 ml of fuel to go 260km, or my 40,000ml tank will take me 40000/36 = 1100km.

[doikor]

> The numbers don’t work out too, “litres per 100km”. Why not millilitres per km (or litres per gigametre)

> I drive X miles (or X km), I then fill up with Y litres (or Y gallons)

This isn't what most use the liters per 100km for though. People just fill up whenever the light on the car tells them to. Mainly the number is used to compare cars when buying a new one. Some keep track of the actual consumption to notice if something is wrong with their car (just write down the current number on the odometer and how many liters you put in on some paper/app/whatever. you can do the actual calculations later)

At least this has been my experience here in Finland.

[manholio]

> If I need to travel 260km at 20km/litre I need to but 260/20 litres or about 13 litres.

> With the “metric” way you need to do two calculations.

That's really an absurd way of looking at it, because one of those calculations is a division or multiplication by 100, and 100km happens to be a typical distance someone might be interested into finding fuel efficiency.

So the answer to me is an immediate mental computation, 2.6 x 5l = 13, you never ever need to compute consumption per km, express things in ml etc.

Your own "easy" examples look to me very intuitive and convoluted, so I guess the systems are 100% comparable, the only difference is the power of habit.