I was looking through the threads to find out about this myself. From what I gather the best advice is to just use Longlife oil (VW 504/507 spec) for best protection, such as Castrol Edge 5w30 as suggested. I saw 4 ltr bottles in ADSA for £30 or £36 (can't remember). As long as it says on the bottle it conforms to VW 504/507 spec you should be ok.