More than you ever wanted to know about motor oils - in this case spefically for air cooled porsche engines -

Oils: What oil do I use in my aircooled Porsche or VW?

The short version is that oil reformulation has taken place over the past two years because of mandated cut backs in zinc (Zn) and phosphorus (P) that makes up the anti-wear additive ZDDP, zinc dialkyl dithiosphosphate. That means you will get faster wear.