Novema,
As a correction to first post, please take note:
Compressor Series 2 in Europe always uses sintetic poliol ester oil (SR30). Recently, in Series 5, they changed for Castrol Icematic SW220HT (desevolved for HITACHI only).
There's no graeter contamination risks between them. A good vacuun it's enought. Consider possibility make your gas retrofit by the overhaul stop.
Stay cool