What is Dielectric Grease?

Mike Howells
Mike Howells
A tube of dielectric grease.
A tube of dielectric grease.

Dielectric grease is a non-conductive, silicone-based grease that's designed to seal out moisture and prevent corrosion on electrical connectors. It also disrupts the flow of electrical current, which makes it good for lubricating and sealing the rubber parts of electrical connectors. It's commonly used in automotive spark plug wires, recreational and utility vehicles, and electrical systems in aircraft.

Physical Properties

Mineral spirits, which can dissolve dielectric grease.
Mineral spirits, which can dissolve dielectric grease.

This material is a translucent, gray lubricant that does not dissolve in liquids like ethanol, methanol, mineral oil, and water. It can be dissolved with Methyl Ethyl Ketone (MEK) and mineral spirits though. Dielectric grease affects silicone rubber over time, so it isn't always a good choice to use it on silicone-based O-rings or wiring harnesses.

It can withstand high temperatures, making it a good choice for engine compartments and similar locations. Many dielectric greases are rated to work in up to 392° F (200° C) temperatures, and some can operate at up to 500° F (260° C). Though there are other greases that can work at these temperatures, they may not prevent the flow of electrical current like dielectric grease does.


Dielectric grease is often used in spark plug wires.
Dielectric grease is often used in spark plug wires.

Dielectric grease is widely used as a sealant for spark plugs in gasoline or diesel engines, as well as on the gaskets of multi-pin connectors in the electrical systems of vehicles and boats. When used with spark plugs, it's applied to the rubber part of the plug wire. This helps the boot slide onto the plug's ceramic insulator and keeps dirt or moisture from contaminating the seal and disrupting the electrical current.

Dielectric grease will not dissolve in methanol.
Dielectric grease will not dissolve in methanol.

Besides being used to seal rubber covers on electrical connections, dielectric grease also prevents corrosion when applied directly to metal connectors. Though it works well for this purpose, it can sometimes cause a connection to stop working if not all of the grease is pushed out of the way between the points of contact inside the connector. Additionally, it is often used to lubricate other engine-related parts, like rotors, distributor caps, and speedometer cables. It can be used in other situations where electrical connections may be exposed to moisture and dirt as well, like outdoor lights, satellite TV installations, trailer hitch wiring, and battery terminals.


Dielectric grease can be used to lubricate a distributor cap.
Dielectric grease can be used to lubricate a distributor cap.

Silicone-based lubricants, including dielectric grease, can irritate the skin and eyes, so users should wear safety glasses and gloves when using it, and should wash any skin or clothes that come into contact with it promptly. At high temperatures, it may create formaldehyde, which irritates the eyes and respiratory system, and is associated with cancer. Those buying this product should consider the temperature conditions in which they need it to work, since some formulations are better for higher temperatures than others.

Grease and lubricants in general can ignite and burn when they're exposed to a lot of oxygen. This is a particular risk when they are used in medical devices, pressurized air systems, or oxygen systems in aircraft. This type of grease should never be applied to the threads of oxygen cylinders or valves used on oxygen systems, since the rapid reaction between it and the oxygen could cause an explosion or fire. In addition, most greases can affect paint and coatings on machines or vehicles if left on for a long time. Any excess product should be cleaned up, including any that's spilled on floors, to prevent a slipping hazard.

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Discussion Comments


It can be used in when making splices. Apply some, then use heat shrink to cover. The heat shrink will compress and squeeze out any excess grease, leaving you with a water tight splice! Also, when did diesels get spark plugs?


Spark plugs on a diesel?


So the grease should be applied to the outside of the connection and not between the connecting surfaces?


Shaving cream is non-cutting. It does not damage hair or skin. Yet it helps the blade of a razor make proper contact with your face and hair to give you a closer, safer shave.

Dielectric grease does the same for electrical contacts. It keeps the surfaces in better condition, allows the mating surfaces to touch without scraping badly and thus gives you a better connection *while* keeping contaminants from destroying the connection over time.


I've watched marina electricians dab dielectric grease into the wire hole on crimp-on terminals, and on the stripped end of the wire that is going into the aforementioned crimp-on terminal, then the wire and the terminal are crimped together.

When I questioned the electricians about their procedure, their reply was that was the procedure stipulated by the electrical component company. The dielectric container made no mention of reduced electrical conductivity; the electrical component company's tech department mentioned only the sealant properties, with no mention of reduced conductivity. Which is right?


@anon303343: Electrical connection problems are usually the result of poor or improper connections, period! How does the electrical connection get "poor?" Corrosion, initiated by moisture. To eliminate moisture from getting to the electrical connection, first start with clean metal surfaces. Apply the grease sparingly to the adjoining surfaces. Make the electrical connection. Regardless if this is a set of pull/push contacts or spark plug wires. The metal to metal contacts will displace any grease that touches them. Electric charge passes from metal to metal. The grease simply keeps moisture from penetrating the connection and thus prevents corrosion.


I am also confused about dielectric grease being "non conductive" and "disrupting the flow of electrical current".

Surely,if you are having electrical connection trouble, this would be the last thing you would want to use. Enlighten me.


It does not "enhance" the electrical connection directly, but it can help "push" or "smear off" most of the debris, dirt, and corrosion on metal-metal connections. I've seen this work on many occasions and I've never seen it do more harm than good.

The problem is just the price at $5 a tiny tube, whereas you can pick up a big can of contact cleaner for the same price. The contact cleaner, however, won't leave a residue, or in this case grease, to seal out humidity and dirt. Best to use both unless you're lazy like me.


It's also used on the threads of valve stems with TPMS (Tire Pressure Monitoring Systems) to prevent corrosion,and breaking off the valve stem in the cap.


anon111410: Because it is non-conductive, if you put it between two mating surfaces, the electricity cannot conduct through it from one surface to the other.


I drive a Dodge caravan and it has electrical problems, the wires have been all covered with electric tape, but it acts up when it rains. can I apply dielectric grease for the problem?


I have greens mower with a starter solenoid that keeps going bad. I think it's water causing the problem. What if I smeared dielectric silicone all over it. Nothing would short right? These solenoids are $135 a piece.


if its non conductive how can it get in the way of the contact between two mating surfaces if used sparingly?


Can dielectric grease reduce friction between terminal and pin inside a connector?

Can dielectric grease reduce or eliminate fretting on the terminal?


@googlefanz -- This is a common misunderstanding. Like you said, it is not conductive, and therefore does not enhance the conductivity of a connection. What it does do, however, is help keep the connectors in good shape, that is, free of corrosion, debris, etc.

Clean connectors obviously work better, so by keeping the connectors clean, dielectric grease does play a part in enhancing conductivity, albeit indirectly.

Again, as you said, the grease itself is not conductive, but keeps the parts that are conductive in good shape, so in the end the overall conductivity is enhanced.


So I'm kind of confused. I know dielectric grease is non-conductive, but a lot of people on different sites seem to be saying that it improves the conductivity of spark plugs, boat lights etc. Can someone explain to me why it would do that if it is not conductive?


A quick note on using dielectric grease for spark plugs. It works great, but you really have to be careful to make sure the grease doesn't get in between the two contacts (i.e. mating surfaces), which can reduce their conductivity.

This usually isn't a problem as long as your contacts are clean beforehand, and you don't just slather the grease on, but it's just a little something to watch out for, particularly for first time users. As always, follow the instructions, and if in doubt, ask someone who knows.

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    • A tube of dielectric grease.
      By: cristi180884
      A tube of dielectric grease.
    • Mineral spirits, which can dissolve dielectric grease.
      By: Coprid
      Mineral spirits, which can dissolve dielectric grease.
    • Dielectric grease is often used in spark plug wires.
      By: zorandim75
      Dielectric grease is often used in spark plug wires.
    • Dielectric grease will not dissolve in methanol.
      By: Nico Armbrust
      Dielectric grease will not dissolve in methanol.
    • Dielectric grease can be used to lubricate a distributor cap.
      By: Duncan Noakes
      Dielectric grease can be used to lubricate a distributor cap.