What oil additive do you recommend to stop leaking valve covers? 1998 Subaru Forester
Those type of products don’t work on valve cover gaskets. If the gaskets are leaking they require replacement.
Tester
I’d just replace the valve cover gaskets. Oil additives are hit or miss. New valve cover gaskets will work 100%.
Sometimes just carefully tightening the fasteners that secure the covers works too…Just good and snug. You don’t want to crush the soft gasket and deform or crack the cover…
This is a very easy repair. It should not cost you more than $100. There is no additive that will repair a valve cover leak. If there ever is one, avoid it.