Dielectric Grease

Dielectric grease is a silicone grease that seals electrical connectors against moisture and corrosion. Here's how to use it and our ranked picks.

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Dielectric grease is a non-conductive silicone grease that seals an electrical connection against moisture and corrosion without ever touching the metal contact itself — despite the name, it does not conduct or boost a connection, it just keeps water and air out of the gap around it. Pack a thin coat inside spark plug boots, trailer light connectors, headlight and taillight bulb sockets, and battery terminal boots before you reassemble them, and the seal holds for years. It earns a permanent spot in the toolbox if you live somewhere winters mean brine on the roads, tow a trailer, or do your own bulb and plug changes; a small tube outlasts most of the jobs you'll use it on. Picking a dielectric grease mostly comes down to format, not chemistry — most name-brand automotive greases perform about the same, so a syringe or brush-top tube that lets you control a small dab on a spark plug boot or bulb socket is easier to work with than a large tub. Apply it sparingly: a thin film on the connector or inside the boot is enough, and any excess squeezes out when you seat the connection. It is not a fix for a contact that is already corroded — clean the metal first, then seal the joint with dielectric grease on reassembly — and it is not a substitute for anti-seize on threaded fasteners or a general-purpose grease on moving mechanical parts, since it is formulated to seal, not to lubricate under load.

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