Valvoline Premium Blue for Soot

[Rushin5]

Reason being, my 2250 that has 660k is now leaking combustion gases into the coolant and my 2350 recently had an overhaul and I'd like to preserve (if at all possible) or at least extend engine life without demandating.

Another option I want to try with my 870 is a product called Engine Restore, or Marvel Mystery Oil. Anyone have any experience with those?