Kilometrage seems a bit clunky, is it acceptable though? Anything better?
Couldn’t find anything - found “mileage” used with kilometers in both India and New Zealand:
And I don’t understand German - so can’t say for sure, but looks like they use “Fahrkostenzuschlag” or “Kilometergeld” neither of which seems “better” 
FWIW, in Spanish we use the word “kilometraje”.
What specific meaning of ‘mileage’ are we looking to substitute?, because the word has several meanings
E.g. ‘low mileage used cars’ means cars that have driven a comparatively low total of lifetime miles, whereas ‘your mileage may vary’ is talking about fuel economy (miles per gallon)
We’re mostly metric in the UK, but still use miles (and in the case of fuel economy, still often talk about mpg, even though fuel is sold in litres). People generally still use ‘Mileage’ as a vague multidefinitional term.
Very generally though, terms like this may tend to give way to more directly meaningful, unit-agnostic terms; for example ‘length’ instead of ‘yardage’ for measuring cloth.
As Mangetout said we need the specific meaning of mileage that you refer to.
In German the terms for the varous meanings of mileage mostly do not refer to an unit e.g. Kraftstoffverbrauch for fuel consumption. But: Kilometergeld for a distance-related reimbursement.
Here in Québec, the French term is kilométrage, but in everyday parlance people (especially older folks) still use millage when talking about distance, wear and tear, etc.
Note that because the units are inverted to litres/100 km (less is better), “gas mileage” is not the proper concept. People talk about consommation [d’essence] ("[fuel] consumption") instead.
Well, in English Canada we still say mileage. There’s no such word as kilometerage.
We tend to understand miles per gallon better than litres per hundred kilometers too. Although the latter is slowly gaining in popularity.
Litres per 100km = 0.1m[sup]3[/sup]m[sup]3[/sup]/10[sup]5[/sup]m
= 10[sup]-2[/sup]m[sup]2[/sup]
Thus the metric (non-SI) unit for mileage is the micro Hectare.
In Hebrew we say the same, albeit with a different accent, probably.
However, that should be 1x10[sup]-3[/sup] m[sup]3[/sup] / 1x10[sup]5[/sup] m = 1x10[sup]-8[/sup] m[sup]2[/sup] , I think, so it’s a pHa (picohectare).
Fuel economy was what I initially had in mind but since you’ve brought it up, now distance as well.
farage.
I don’t have an answer, but in the process of googling for one, I found this piece of exciting trivia which I must share:
http://www.arizonahighways.com/?q=blog/interstate-19-miles-or-kilometers
Don’t hectare the OP. It was a good question.
I think it’s obvious that this will join the many words in English that are literally absurd or obsolete but have acquired a specific meaning larger than the sum of the word-parts. Dial me up and I’ll explain it further, if necessary.
In German:
in the sense of fuel economy: Kraftstoffverbrauch (see note 1)
in the sense of distance covered by a vehicle: Tachometerstand (see note 2) or Kilometerstand
(1) as noted above by others, fuel consumption is measured, as in a lot of other countries, as fuel volume per distance covered (l/100 km) rather than distance covered per fuel volume. IMO this makes more sense - in the overwhelming number of cases fuel economy relates to the question ‘I drive a given distance per year; how much fuel do I need to budget for?’ rather than ‘I need to cross this desert, can I cover the distance with the fuel I carry?’
(2) false friend: in German the tachometer is the instrument for vehicle speed + total distance covered rather than the instrument for engine speed.
The convention in metric is to use a unit-less descriptor (like you did above where you said ‘distance’). A good example of this is land area: acreage in old money, but just ‘area’ in metric.
I think we should use: “distance duration” for metric-speak. .
Probably bad examples. Both are countries which converted from Imperial to Metric. The old colloquial terms are still in use probably, they are certainly in Pakistan (admittedly, we are not fully metric still, despite having switched officially 30 years ago).
That struck me as surprising since I tend to make “can I cover this distance” type calculations more, than I make “how much fuel for this distance” calculations. Maybe it’s the former military in me, in a specialty that was all about vehicles, that makes me an outlier. For long trips I tend to plan to make brief stops every 1.5-2 hours for safety’s sake. Things like heavy traffic and unplanned stops because I need the bathroom sooner than a normal break window change the plan. As a result, I tend to end up mentally recalculating time-distance and fuel factors repeatedly in the course of long trips.
I would say economy or, if context isn’t clear, fuel economy. Some friends say consumption.