What is dielectric grease ?

[cbriden]

This is a mysterious substance to me. People use this stuff on electrical bulbs, battery terminals, spark plug boots, ect. I have even heard of using it on the spark plug threads instead of anti-seize! I just don’t understand how a “dielectric” which means “nonconductive” grease improves electrical connectivity.

A specific example would be:
I have a 2000 Ford Expedition with coil on plug ignition. Say I wanted to change all the plugs out. Would coating the spark plug threads with dielectric grease be a good idea or a bad one ? How about coating the tip of the spark plug? What about putting a blob of it into the boot on the coil cap?

I guess I just don’t understand how this stuff works & why people swear by it. When I did this service I put a very light coat of anti-seize on the plugs and a small blob of dielectric grease into the boot. The truck works OK – just don’t understand why. What exactly is the dielectric grease designed to do ?

Topic

[Mike Graham]

As I understand it this grease is designed to keep moisture away from electrical connections and can be used on spark plug boots to aid sliding over the ceramic part of the plug. It is meant to keep moisture out of electrical plugs etc. but is not meant to be smeared on electrical contacts, apart from on battery terminals after they have been cleaned and tightened up. Smear some grease on the top and sides of the terminals/connectors to prevent corrosion, but do not get it between the battery posts and clamps. Hope this helps. Mike

[Steffen Nyegaard]

http://en.wikipedia.org/wiki/Silicone_grease

Last paragraph. Basically, it is bad if the connectors are not spring loaded enough to penetrate the grease, but good for protecting against oxidation.

[ridinred24]

We have several service bulletins from acura telling us to pack connectors with it to drive out/prevent moisture and corrsosion in connectors. If im dealing with corroded or burnt terminals or connectors i usually repair them then pack them with the dielectic grease

[Rick]

I don’t see how it would help on spark plug threads. The reason you would use dialectric, non-conductive grease in a wire terminal is so it doesn’t short a multiwire connector.

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