Porsche A40, C20, C30, C40 and C40 GT Engine-Oil Approvals Explained
Porsche oil codes identify manufacturer approvals, not just oil thickness. This guide explains the practical meaning of A40, C20, C30, C40 and C40 GT, why two 0W-40 oils may still be unsuitable substitutes, and how to verify the correct approved product for a Porsche engine.