To clarify my earlier post, I meant of course that a single bottle of oil is enough for the refill (between 3 and 4 litres) and more than enough for any top-ups for the about 30000 km before the car starts to remind of the end of the “Long Life” maintenance cycle. Oil is certainly not up there when it comes to costs of owning a small car, ICE or not.

A cursory look at used oil: it's still rather like the stuff that goes in, albeit black, of course. Without specific tools, I think it's impossible to tell it apart from oil that's used for, say, 10000 km.