Do esters make gaskets swell?

[Ken4]

I've heard esters help seals swell to prevent leaks, what about gaskets? Specifically the Valve Cover gasket.

 

[crashz]

Seem to. My GF's beetle had a valve cover gasket leaking like a siv. It has since stopped after the AutoRX. The esters must have swelled it closed.

However, on my truck I'm getting a little oil weeping from the head gasket. Not much, but enought wet the starter. This hasn't changed after AutoRX, so I think only rubber gaskets are affected by esters.

 

[MolaKule]

Nitrile seals (synthetic rubber seals) and composition gaskets of rubber and cork may swell slightly under ester oils. If it's pure cork, forget it.