Can I use kilometers, litres, or L/100 km?
Yes. Open Mileage → Settings (the gear) → Units. Distance can be miles or kilometers, and fuel economy can be mpg (US), mpg (UK), L/100 km, or km/L. Auto follows your device's region. Fuel is priced per gallon with mpg (US) and per litre with every other choice. Currency follows your device's region. Changing units only changes how numbers are shown; your trips aren't altered.