JE Engineering P38 S560 - some questions

[996TURBO]

Hi,

A friend of mine bought a JE Engineering P38 and i have some questions.

I need to do full service on that car.

What kind of oil should we use?

JE recommends Castrol Magnatec.

Today i can only find 5W40 or 5w50, not sure it's a great idea in a old engine.

Thanks for your help.

Florent