Many times oil leak comebacks are caused by the use of silicone or some other type of sealant coating that is used with the gasket.
Newer, high-tech gaskets, in many cases today, require no sealer at all, just a clean dry surface, proper torque and good mating surfaces. Intake manifold applications may require a very thin layer of RTV sealer around the cooling passages if they are pitted.
Cork gaskets may also require a small amount of RTV sealer to make up for imperfections in the sealing surfaces. In the old days guys put cork gaskets in warm water to make them swell a bit before installation. Just remember: don’t over torque!
Urethane steel reinforced gaskets should not be used with any sealers. Just torque to manufacturer’s specs, and if the parts and sealing surfaces are clean and not damaged you’ll have a good seal.