Major Service + Extras - Self Imposed...

[Diesel_vert]

Using oils that are thicker than necessary (in a healthy, well functioning engine) might result in higher operating temperatures and reduced fuel economy & responsiveness due to increased friction. Also, in the case of HPR 10, it's not as free-flowing when starting up from cold.

Does the VW rating not make it useable? especially for an older car?

No, no, you can still use it, but it's my opinion that a 50-weight oil is too thick for your engine - but you certainly won't damage it.

What would/could that do?

This...

I would use the HPR5 5W40. Use HPR10 only if the engine uses too much of oil.

If we're sticking with Penrite, I too would recommend HPR5 5W-40 over HPR10.