The specific formulation of dielectric grease allows for many typical mechanical electrical connections to 'penetrate through' the grease down to the base metal connection. The areas around the point connections are sealed off from atmosphere to prohibit corrosion or tarnishing that would otherwise eventually increase the contact resistance. This formulation also will not harm many plastics or rubber compounds as well as tarnish platings like tin, silver, or copper.

While the base grease is an insulator by itself (i.e. if sandwiched between two conductive plates), it is not 'permanent' enough to get in the way of contact mating surfaces with high mechanical contact forces and small surface areas - such as pin/socket contacts, knife contacts, blade contacts, setscrew contact, etc.). 

While you would use Dielectric Grease on relay pin contacts, you would not use it on the actual relay contact surfaces (due to potential arcing or large contact surfaces with low contact pressure).

Standard, translucent dielectric grease is widely used in automotive connectors, marine electronics, or other applications where moisture and corrosion on mechanical contacts would adversely affect contact resistance. The other factor is the type of connection and how close the other connections are. 

A gas tight, static, and mechanically sound electrical connection technically would not need any grease. The primary purpose of the grease is to prevent oxidation and to lubricate.

Gold plated contacts, which do not corrode and have a very low contact resistance, have limited wear resistance. However, gold plating is also not practical for many applications, and some lubricant may still be needed to reduce wear on the contact surfaces. In this case, dielectric grease would be an option.

However, dielectric greases will not technically "improve conductivity" as they do not add contact area or contact pressure to the basic contact joint. This is where conductive filled greases come into play. The conductive grease technically adds to contact area, and also can lubricate moving parts as well. The result may be a lower contact resistance, but not necessarily resulting in a higher current carrying capability.

With regards to a lap joint on a busbar, a conductive grease or anti-oxidant would be the best choice. Same thing goes for an aluminum setscrew lug. However, you would not use conductive greases in applications where the adjoining contacts are close enough for excess grease to cause 'bridging' between circuits (especially low voltage & current applications <1V & <10mV). 

In an application of a crimped butt joint on a single conductor, application of either grease would suffice and not cause any issues - as long as the compounds don't affect the insulation near the joint.

Contact resistance is basically a function of contact surface area, contact point pressure, metal conductivity, and cleanliness. The more contact area and pressure provided, combined with increased contact cross-sectional area, will allow more current to pass without heating up the contact area.

Dielectric, as a term, refers to an insulating compound, as in capacitors there is a dielectric compound, layer, foil between the electrodes.

A connection may be coated with a lubricant in the case of moving contact to prevent it from seizing and welding. The conductive qualities of that compound would be unimportant, it could be either high or low as the compound's function is lubrication, not conduction. The connecting surfaces must have sufficient wiping action to actually clear the compound away from the actual conducting surfaces.

(I think it is needless to say that any greaselike compound will be less conductive than solid metal.)

A stationary connection may be coated to prevent the contact surfaces' corrosion. The conductive properties would be immaterial to the primary function of the compound in this case as well.

Hope that helps S”plain things, know it did for me as I was curious as to the property of dielectric grease, hope you didn"t kark from reading..

Will

Dielectric grease is particularly useful in any marine environment and actually anywhere being directly exposed to the elements (like motorbikes are) - if not used you will find connections will show signs of corrosion after just a few weeks.

It is true that you can cover pin/socket connections for example, with dielectric grease, the pin moving through the socket interferance fit will remove enough grease to ensure good conducting metal to metal contact. The whole idea is that the immediate surroundings of the actual connection remain coated with a layer of protecting grease.