No, the opposite: it is an insulator, which is what the word dielectric means. That is why it is applied around and over connections to seal out moisture rather than between contact surfaces to improve them. The metal contacts must still touch each other directly. On low-current or low-force connections in particular, a film trapped between mating faces can prevent conduction entirely and cause the fault it was meant to avoid.

To the seal, the boot and the outside of the housing, so water and dirt are excluded from the cavity. On a spark plug boot, apply it inside the boot where it grips the ceramic, which also stops the boot bonding to the plug. Let the terminals themselves mate directly. If a manufacturer's instruction specifies packing the connector body, follow that, but do not extend the practice to connectors generally.

Because it does not attack them. Mineral oil based greases cause many elastomers to swell, soften and lose sealing ability, and can craze some plastics. Silicone fluid is chemically compatible with most rubbers and plastics, so it lubricates and conditions O-rings, seals, valve stems, plastic gears and sliding plastic parts without degrading them. Always confirm compatibility with the specific elastomer, since silicone rubber itself is one notable exception.

Not as a general substitute. Silicone greases have poor load-carrying and anti-wear capability compared with lithium, lithium complex or extreme-pressure products, and a heavily loaded rolling or sliding metal contact will wear rapidly on silicone. Use it where compatibility with rubber or plastic, wide temperature range or electrical insulation is the requirement, and use a conventional grease where the requirement is load.

Silicone has very low surface energy and spreads readily, and even trace amounts on a substrate cause paint to withdraw from the contaminated spot, producing craters known as fish-eyes. The contamination is easily transferred by hands, rags, gloves and airborne overspray, and it is extremely difficult to remove once present in a workshop. Silicone products should be segregated from any area where painting, bonding or coating is carried out.

Considerably wider than most mineral-oil greases, typically from well below freezing to around 200 °C or higher depending on the formulation, with good stability at both ends. This is one of the main reasons they are chosen for seals and connectors exposed to weather and to engine bay temperatures. Confirm the range against the specific product, and remember that wide temperature capability does not compensate for the limited load capacity.

They overlap. O-ring grease is formulated specifically for conditioning and sealing O-rings in valve components, and plumbing grease is a water-resistant product for taps and fixtures, both of which are frequently silicone based. This category covers silicone and dielectric greases generally, including electrical sealing use. Where the application is specifically an O-ring in a valve, or a plumbing fixture, the dedicated product is usually the better match.