Probably Ravenol VSE. but it's something that you won't find when you're in a bind. You would have to order it from Blauparts or Amazon508 is a mid/low saps low HTHS lubricant other than its LL properties, possibly cleaning and stay in grade - close to an ILSAC R.C. Lube.
Are some VAG 508 00/509 00 choices a true iv/v synthetic ? Possibly, though I do not recall at this moment.