Gray green substance under oil cap - Cummins ISX15

[SupVit]

Yes, this will be right way to save engine. I saw on the forums, you told people many times to use this method.
What does this substance smell like? There is no smell of coolant. Smells like diesel engine exhaust + hot oil.
Asking because I don't see change of coolant level, color of coolant, oil level. Nothing. But substance appears fast.