Oily substance in intake manifold

[bavArian]

Hello guys,


today I changed the old, warped manifolds for new ones. While doing so I noticed an oily substance trapped below the valves in block and intake manifold. It's only on the intake-side, the exhaust-side is clean without any traces of oil or other residues.



I do not have any steam from the exhaust (neither blue nor white) so I don't think it's from the piston rings / cylinders. I do however add special oil (probably similar to your MMO) to the fuel. Is it possible that a mixture of around 1:150 - 1:200 can cause this?
If so I will drive a tank without the oil and then significantly reduce the amount of oil I'm adding to the fuel.


Thanks and have a nice day,


Daniel