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Well for instance I opted years ago to change my 78 Merc 3.3L valve cover gasket from the specified cork, to a FelPro rubber gasket & when I sold the vehicle last spring, that rubber gasket were still on the vehicle & was tight, with no weeps or leaks.
Changed the 94 Taurus AXODE OEM cork tranny pan gasket to a reusable rubber FelPro one, 10 years ago & it's still pliable & tight.
Cork is inexpensive, dries out & can flake off & clog up something important in our lube system, so that & not having to constantly replace the cork gaskets, is why I prefer opting for a quality vendor rubber gasket.
No matter which you opt for, Don't opt for an inexpensive no name gasket vendor, use a quality part.
Cork is the reason every V-6 Ford Ranger had oil leaks. The German Ford engine used them for the rocker covers. The problem is that it shrinks. Viton is a type of synthetic rubber that you want, if you can find it. Even Corvair engines are oil tight with Viton seals.