Dielectric Grease v Chassis Grease

[Joe C.]

One of the most important electrical junctions on C2/C3 Corvettes is at the firewall connectors. Back in the "old days" folks would slather ordinary chassis grease over all the connectors to guard against corrosion. This same treatment would be applied to light bulb bases and their sockets......especially taillights and park lights. Another favorite spot for the chassis grease is the battery terminals. I have been doing this for years, but now I'm starting to look at dielectric grease as an alternative. Dielectric grease is an insulator. I am NOT certain just how well ordinary greases/Vaseline conducts electricity, but people never generally complained of these greases causing a short circuit or current leakage when used on multi connector terminals.

Please edumenicate me as to the advantages of dielectric over other greases (which conduct electricity?). It is confusing in doing a web search as, naturally, there are many different answers to these questions, most of which conflict with each other.

I would prefer to fully encase all electrical connections in the stuff. The only concern here being that if the connection is not good and tight, that the dielectric will insulate the junction. Correctamundo, or not?

Thanks in advance for your forthcoming PITHY replies.

[Terry M.]

Re: Dielectric Grease v Chassis Grease

Joe,

Be careful. I tried to get to the Dow Corning site, but it is a no go from work which is odd because we use cases of their products. My usual field guys are off today for a long holiday weekend, so I can't find out from them -- BUT there is dielectric grease and there is silicone lubricant. One is an insulator (I think that is Dow #7, but can't verify at this time) and one is a semi-conductor (I believe that is the dielectric grease, but I can't find a Dow number for it). Out of the tube they look a lot alike, but do not confuse them.

For what you are talking about you want the semi-conductor. The insulator, while a good lubricant, will not help achieve the end result you want. There is a chance I have a Dow catalog at home, but the wife got after me and I think I pitched all my old catalogs thinking I can find the info on the 'net when I want it.

The down side of any of these silicone products can be explained to us by anyone who paints. I don't know about chassis grease. It will be interesting to hear from some who have used it. What is that yellow stuff that is int he light bulb sockets fo the newer ('80s and '90s) cars?

[John M.]

Re: Dielectric Grease v Chassis Grease

Joe, from our electrical eng. here at work. Note the underlined bit.

"Well, I'm no expert on dielectric grease, but I use it quite a bit with the electrical systems at home. It insulates and keeps out moisture. Prevents electrical connections from corroding and prevents leakage currents from developing (which as you know can keep a spark plug from developing a good spark). It's meant for this purpose. Even though it's insulating, it doesn't hinder the electrical connection - as long as it's a good connection to begin with.

That's the sum of my knowledge!"

[Jack H.]

Re: Dielectric Grease v Chassis Grease

Without getting real specific (exactly what grease compounds are you referring to?) the question can't really be answered.

Silicone dielectric greases come in a variety of formulations. Some are 'doped' with certain impurities to make them thermally active but not electrically conductive (eg, those rifle shot for electronic heat sink usage).

Others can be doped to make them electrically conductive. But, these are 'speciality' items and not the run of the mill dielectric grease you see at Radio Shack or what you get at the auto parts store for lubricating spark plug wire boots.

The 'common' silicone dielectric grease is non-hardening and rather inert to both heat and electric current flow.

Traditional axle grease is also on the low end of the scale in terms of electrical conduction. That's ESPECIALLY true in a traditional automotive application where we're only talking about 12 VDC electric systems. But, it can harden over time making things like lamp removal a bit challenging.

The concept of using a form of 'grease' in an automotive ohmic contact situation is pretty simple. It flows easily to allow bona fide metal to metal contact AND it surrounds the ohmic contact junction to thwart air infiltration and contact surface oxidation...

[Dick W.]

Re: Dielectric Grease v Chassis Grease

The majority of you run of the mill chassis greast is lithium soap based. I will dry out and harden over time, offering no corrosion protection at that time. Dielectric, such as you buy in the auto parts house, will last a very long time, providing corrosion protection. We started using it in the trucking industry in the '60's and where it was used eliminated wiring oxidation. Wonder why new cars have it in all the connections, lamp sockets, etc?

[Pat M.]

Re: Dielectric Grease v Chassis Grease

I will dry out and harden over time

Dick we're all getting older, but don't be so hard on yourself!

[Joe C.]

Re: Dielectric Grease v Chassis Grease

Joe,

Be careful. I tried to get to the Dow Corning site, but it is a no go from work which is odd because we use cases of their products. My usual field guys are off today for a long holiday weekend, so I can't find out from them -- BUT there is dielectric grease and there is silicone lubricant. One is an insulator (I think that is Dow #7, but can't verify at this time) and one is a semi-conductor (I believe that is the dielectric grease, but I can't find a Dow number for it). Out of the tube they look a lot alike, but do not confuse them.

For what you are talking about you want the semi-conductor. The insulator, while a good lubricant, will not help achieve the end result you want. There is a chance I have a Dow catalog at home, but the wife got after me and I think I pitched all my old catalogs thinking I can find the info on the 'net when I want it.

The down side of any of these silicone products can be explained to us by anyone who paints. I don't know about chassis grease. It will be interesting to hear from some who have used it. What is that yellow stuff that is int he light bulb sockets fo the newer ('80s and '90s) cars?

It looks like ordinary white lith grease, which is all that I ever use for electrical connections.

I spoke to a rep this morning, from Permatex. I explained to him about the white lith grease that I use. He told me to go on using it. Yes, it is also an insulator, so no danger in causing leakage across multi connectors in close proximity, like multi cavities at the fuse block junctions.
I asked him lots of questions, until, finally, I asked him just what the heck is the advantage of dielectric grease over ordinary grease. He stated that there is only ONE, and that is, that it stays in place better, and is more durable than ordinary grease.

[John H.]

Re: Dielectric Grease v Chassis Grease

I remember when Packard Electric introduced it in the engine and forward lamp harness multiple connectors that attached to the engine side of the fuse block (and I'm sure Bill Clupper will too). It was around '69 or so, and the stuff looked like green slime paddled into the connectors; the guys that installed the harnesses and the guys that connected them to the fuse block raised hell about getting it on their clothes and hands, resulting in the usual flood of health & safety grievances.

[Dan D.]

Re: Dielectric Grease v Chassis Grease

Silicone dielectric grease provides excellent moisture and corrosion protection, and it does not go away or harden like chassis grease will. It will work fine as long as there is sufficient pressure between the mating surfaces to insure current will 'punch through' the dielectric and provide good electrical contact. Remember, it is dielectric, so it has to punch through in order to work. It will cause all kinds of grief if there is insufficient contact pressure. A screw in light bulb, or even one with fairly strong clips usually work fine. -Dan-

[Joe L.]

Re: Dielectric Grease v Chassis Grease

One more thing: the hydrocarbon components of chassis grease will deteriorate (slowly) certain types of rubber and plastic. The silicone dielectric grease will not.