One litre per mil is exactly 10 litres per 100 km. The Scandinavian mil is 10 kilometres, so the conversion is a single factor of ten — and it is the fuel economy figure every Swedish and Norwegian driver actually quotes.
About the units
Sweden and Norway measure road distance in mil, a unit fixed at exactly 10 kilometres at metrication, and fuel consumption follows the same convention: litres per mil rather than litres per 100 kilometres. The numbers that result are conveniently small — a modern car uses 0.5 to 0.8 litres per mil where the rest of Europe would say 5 to 8 litres per 100 km. Both are consumption units, so lower is better in each, and the conversion between them is purely a matter of which distance unit sits in the denominator.
The exact factor
The factor is exactly 10, since 100 km is 10 mil. So 0.6 l/mil is 6 l/100 km, and 9 l/100 km is 0.9 l/mil. Converting further to American mpg means going through the reciprocal: 235.215 divided by ten times the litres-per-mil figure. A car at 0.7 l/mil is 7 l/100 km is 33.6 US mpg. Swedish company car and mileage allowance rules are written per mil, so the conversion appears in tax calculations as well as at the pump.
Where you meet this conversion
Swedish and Norwegian motoring throughout: car reviews, manufacturer specifications for the local market, fleet policies and tax rules all use litres per mil. Anyone comparing a Swedish road test to a European manufacturer figure needs the factor of ten. Electric vehicles follow the same pattern, with consumption in kilowatt-hours per mil in Sweden and per 100 km elsewhere, and the same tenfold relationship applies.