Di-electric grease is an insulator that is particularly useful on integrated circuit boards when a component is slid-onto a contact-surface or placed-on/in a contact-connector slot.
As 52Carl posted : "A film of it between tight clean connections gets out of the way resulting in no loss of voltage nor added resistance, while providing corrosion prevention." It not only gets out of the way, it allows a metal-to-metal connection and keeps corrosion/oxidation out-side-of the connection/contact point.
At high voltages anything will most likely conduct?
http://www.wisegeek.org/what-is-dielectric-grease.htmSo, if that author is correct, di-electric grease should not be used between modern-engine spark plugs and ignition-wire ends, especially if it is silicone rubber?
The added "conductance" of supposedly conductive metal-containing anti-oxidant greases is also questionable/marginal. They are, however, anti-oxidizing compounds. I use them on all my 6v battery leads connections.
