I know you mentioned that all your seals were Mazda OEM but I only found success with a Mazda valve cover gasket and CAS o ring. Aftermarket kept leaking. OEM is stupid expensive where I am but I had no other choice and it seems to at least cause oil "sweat" instead of leak.
Reviews of OEM Mazda valve cover gasket
15 votes
Definitely a bad valve cover gasket. I changed my spark plugs a couple months ago and I had hella oil on my 4th spark plug. Replaced the valve cover gasket and it fixed my issue 100%.
OCV gasket oil leaks on my 2014 Mazda6 SkyActiv valve cover.
From experience the only valve cover gasket I've used that doesn't leak is the OEM Mazda one, so I'd recommend one of those (worth the money!!)
Smart to get the Mazda OEM valve cover gasket. It is much better quality than any of the aftermarket brands I've seen.
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