In message tonline,
Roy Lewallen writes




And, when tightened threads *are* necessary for electrical contact, oil
or light grease often improves conductivity. Thread pressure is
adequate to squeeze the lubricant out from the contact areas, allowing
good metallic contact. And it prevents oxidation or other corrosion of
the contact surfaces when the contacts are moved or vibrate by
excluding air. This holds true for all contacts properly designed to
wipe and contact with sufficient pressure. Quite a few people
incorrectly attribute this improvement to conductivity or some mystical
property of the lubricant, but its real trick is simply to exclude air.

Roy Lewallen, W7EL

I would be surprised if a lubricant was sufficiently viscous and had
enough 'body' to act as an insulating layer between two parts of
well-tightened a connector.

However, I have personal experience that Araldite can. This was used to
ensure that a reducing bush (PG11 thread to 5/8"), in the wall of the
housing of a CATV amplifier, remained securely in place. On all four
ports, there was absolutely no continuity between the outers of the
connectors and the housing.
--
Ian