General question: replacing gaskets/coat them with oil first?

[My Nameis]

I’m curious if you should always coat new rubber gaskets with a thin layer of oil before assembling.

I know doing so helps with the installation and reduces any binding, but wouldn’t it cause a wicking effect and create leaks?

Topic

[Lorrin Barth]

My experience is that if you put any sort of lubricant on rubber gaskets, when you torque the fasteners, the gasket comes slithering out. My recommendation would be clean surfaces, clean gasket – everything dry.

[Austin]

agreed with barney. Adding oil can make it a pain to keep the gasket in place as well. Sometimes I go as far as using gasket adhesive and spray it down so it will stick.

[Bill]

Only use oil on rubber O rings or as the manufacture specifies.

[My Nameis]

What about things like spark plug valve cover seals?

I replaced a vtec solenoid gasket this summer and upon someone’s suggestion I coated the gasket a bit with oil. It then leaked worse than original gasket.

So I took it apart and made sure everything was as dry as I could get it. No more leak (knock on wood)

But I know some recommend oil so it left me confused

[Lorrin Barth]

I think we are getting lost in terms and definitions.

To me a gasket is flat usually with holes for fasteners.

A seal is something I think of as running on a revolving part such as a rear main seal or a wheel bearing seal. These should be prelubed on the surface that meets the moving part.

O-rings are installed lubricated, usually with grease or some lubricant compatible with the system you are working on. O-rings need to be cut free and lubricant helps keep them free from damage inflicted by a burr at installation.

When you get into spark plugs on overhead cam engines you run into a host of various designs that allow the plug to screw into the head without oil leaking. Things at this location made of rubber, things you want to get apart again without damage like spark plug boots, are lubricated with silicon grease.

In general, if the seal stays in place and doesn’t leak, you did it right.

Technicians often have special opinions about how gaskets should be installed and this basically boils down to the fact that they don’t like using a gasket scraper because it costs them time. They also don’t like RTV for this reason.

[spelunkerd]

Overall I agree with the above remarks. I suspect the idea of coating with oil comes from the general standard to smear a dab of oil onto the gasket for screw-on oil filters. If you don’t do that, there is a risk that the gasket may grab and stretch, distorting the shape of the gasket to resemble that of an oxbow lake from above. You get a radial bulge in the gasket, which could leak. Coating with oil markedly reduces the chance of that.

The other common circumstance where you use oil or grease is when you need to slide a dry shaft through a new seal, and of course that is a similar situation where you could damage the new seal from excessive friction.

For most face to face gaskets, there is no radial spinning or excessive friction before the gasket is seated, so I don’t see any reason to coat those with oil. Opinions vary about RTV, but I never use oil except in the special circumstance of a filter or nut that spins on, possibly twisting the gasket. For example, with A/C gaskets, A/C oil is commonly smeared on new O-ring surfaces at the point where the contact nut and O-ring screw into place.

[Author]

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