Interessante Theorie. Hier die Meinung von Amsoil zu ZDDP:
Do Older Engines Need Oil With ZDDP Additives? - AMSOIL Blog
Using a high-zinc oil with a high dose of ZDDP additives helps protect classic cars and hot rod engines. AMSOIL Z-ROD Synthetic Oil contains 1400 ppm zinc.
blog.amsoil.com