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Proper Use Of Dielectric Grease?

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Pardon my ignorance, but does dielectric grease go not only on the rubber boots/ceramic portion of

the spark plug...but also on the metal conductor contact point as well?


"Dielectric" implies insulator, but I read somewhere that the grease is thin enough so that if used

on tight fitting electrical connections (like distributor cap to spark plus wires), metal to metal

contact is still retained.


Bottom line, should it be used on metal to metal electrical contacts? Thanks!

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this may not be a direct answer to your question, but, i only use dielectric grease on terminal ends of exposed wires subject to exposure and/or moisture, such as grounds, fuse box connections (underside), tail light connections, etc.  i personnally have not used it on spark plugs or associated bits.  i do use never-sieze on sparkplug threads, though. 


and, if you're unfamiliar with the amount of torque when tightening the sparkplugs, use a torque wrench to get a feel for the proper amount of 'grunt' to use.  i always fear overtorqueing and screwing up the threads on the aluminum head.

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Spark plug dielectric grease is primarily intended to prevent high voltage from welding a connector to the metal center sparkplug contact; it also helps prevent rubber covers from sticking to other parts.  It is, in addition, a key item in lamp life tests to make the old lamps can be removed from their sockets when the test is complete.


A good metal contact should be tight enough to push aside the grease when the spark plug, light bulb or even a quick disconnect is assembled or screwed in; the remaining grease will help prevent contact corrosion that could cause an intermittent contact after extended use.  But make sure it does not lubricate a contact point so well that it will shake loose after driving a while.

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Dielectric grease is electrically insulating and does not break down when high voltage is applied. It is often applied to electrical connectors, particularly those containing rubber gaskets, as a means of lubricating and sealing rubber portions of the connector without arcing.


Alright, I stole the above from Wikipedia, but it concisely answers the question. So, what it means is that dielectric grease is good for lubricating rubber or plastic connectors to keep the power (e.g., spark ignition) from leaking out of the connector, particularly when the connector gets wet. In a car, the ignition system is really the only place where high voltage is present, so putting this stuff on the spark plug boots is a good thing (clean the dirt off first). Dielectric grease is good for use on any rubber piece covering an electrical connection, because it will keep it soft and pliable, while not being conductive. There are other products sold as rubber or plastic conditioners that are based on petroleum products,  which are not good to use around electrical connections, particularly high voltage.




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