Hi Dimity!

Differs a lot by engine (PT or ABH) and milage.
Lower end is somewhat like 0,6 l/1000 km which is definitely needed by construction, ok-engines also take 1 or 1,25 l easily, but there are reportedly also engines around which are taking up to 3 litres for years already without allto bad side effects. Of course katalysts do not like to much burnt oil.
Whenever you exceed 3 litres (without just spilling them onto the road) you should start being worried....

Andreas

Es war schon immer etwas teurer, einen besonderen Geschmack zu haben...