I never understood that. Put dielectric on electrical fittings, snow plow etc. and never had a problem. " Dielectric grease can be applied to the metal parts of virtually any electrical connection that will be exposed to the elements to serve as a sealant that protects the connection from contamination and corrosion ."
Opinions vary…
Silicone grease protects against moisture-causing corrosion as well as being a good dielectric. If you apply something to an electrical connection to protect if from corrosion, you want that substance to be a good insulator, so it doesn’t cause current to flow to places it shouldn’t, might run the battery down otherwise. Sometimes silicone grease is applied before making the connection, which seems confusing b/c SG is an insulator. But the electrical connection is made despite the SG in that case, by tightening the fasteners enough to squeeze the SG from the electrical contact zone. SG is good for spark plug boots b/c it makes it easy to slide the boot on, and also helps prevent a high voltage path from forming inside the boot, shorting out the spark.
2 Likes
As do our experiences, mine of which I report objectively.
I also wonder about this. I have never used red rubber grease. I recently discovered it was a thing. Read the description about it’s benefits of using it, and it sounds identical to silicone grease. Except I guess silicone grease might have a higher melting point then red rubber grease. Which got me thinking that if I had a bushing, far from any heat, if red rubber grease or silicone grease was best. Don’t know that there’s really a difference in lubricating properties of rubber, but it does sound like red rubber grease and silicone grease are two different things.
Right… 
If there’s two traits I cannot stand, it’s truthers and deniers. I give my objective experience, and someone thinks they know better than me what I experienced.
This is the last time I will address you in any way. If you take off your combative glasses and re-read what I wrote, without assuming in advance someone is out to get you, you MAY see that I was not attacking you in any way or even disputing your results. In fact I said if it works for you, great. Other people may not like using grease for the reasons cited and there are options available. THAT is my experience and opinion. You are getting mad at me and doing exactly what you accused me of doing. Look back at any of your prior posts regarding obsession with tire pressures and gauges- who was one of the few who contributed to those discussions? At any rate, your true colors are now evident and all I have to say is good day to you- you’ll be one of the few times I used the site’s ignore feature…
Twin Turbo, please understand something: I’ve lived a whole life of not being believed, so I was in defensive mode - as I have been all my life. Sorry if I misread you. Damaged goods as they say.
As for my “tire pressure obsession”, I’m just trying to spread the good word, and some advice.
I found out, through personal experience with people I know, and via surveys I conducted, that tire pressures are distributed this way among the driving population:
40 percent: Underinflated
40 percent: Overinflated(some dangerously so!)
And the remaining 20 percent: Like myself, within 1psi of what the vehicle mfg. specifies on those stickers on door pillars or inside gas filler lids.
That 80 percent are not realizing the full handling and ride potentials of their cars, as I am realizing, and enjoying, even a mundane backroads romp to and from work.
Having a Porsche with 40psi in all the tires when Porsche themselves specify 34 in front and 42 in back makes a huge difference in acceleration, getting through turns, and braking. And I want to share that knowledge with them.
There’s a comedic element to this , as I expect you already know. I bet you’ve had this experience: You recommend something to someone in order for them to prevent a potential problem; they don’t follow your recommendation, and sure enough, they experience the problem. Often they’ll come back to and and say you caused the very problem … lol … Common comedic plot on tv sitcoms, especially both Seinfeld and Curb Your Enthusiasm.
Except for the super-conductors, virtually everything is a dielectric. They have an insulation value vs thickness, much like wall insulation. If you had a foam insulation in your wall with an R-value of 6 per inch thickness, then 2" would give you R-12 and 1/2" would give you R-3. If the foam was only 1/100" is would have an R-0.06. 2" would keep a lot of cold out where 1/100" would be pretty ineffective.
That is the same for dielectrics. At thin film, i.e. the grease that might get between two conductors that are physically touching, the grease does not stop current flow. But for example, if you put a glob of dielectric grease into the boot of a spark plug wire and pushed it onto the spark plug, that very thin film of grease between the surfaces of the conductors will have no opposition to current flow, but the grease trapped between the inside of the boot and the ceramic of the plug is an inch or more long so it keep the spark inside the boot and prevents it from arcing to a nearby ground.
1 Like
I have a tube of rubber grease, left over from a master cylinder recall. Rubber lubricant is great for installing difficult grommets, rubber moldings with tabs etc.
High voltage engineers have the opposite view- there are no insulators, everything is a conductor 
The way the contact interfaces are designed, they scrape away any grease or oxide layers as the connection is made. So normally it is not a concern. This is why they can pack a bulkhead connector with dielectric grease and it still functions properly once connected even for low voltage/current applications.
The grease performs several functions- it seals out any moisture ingress to prevent future corrosion of the terminals and it provides additional insulation. On a spark plug, the designed creepage distance along the ceramic length is sufficient for preventing arcing but applying grease helps keep out moisture, reduces potential for arcing inside the boot (corona formation) and makes it easier to break the bond between the boot and ceramic when disassembling after a long period in place.
FWIW I checked Home Depot for greases and they stock two red greases, both with silicone. IMO you could also call them red rubber grease since silicone is an elastomer. While rubber is technically latex, all elastomers are often called rubber too. It’s like Kleenex and facial tissue.
I don’t know all the smart people proper words for all this, but I do know the end result when the mechanic before you is too LAZY to use a little Dielectric Grease in the end of a COP boot (same result with spark plug wire boots) and I just want to hurt them bad… lol
The beginning of the oh crap moment…
The I’m REALLY irritated at this point…
And why they needed replacing in the 1st place… lol
A very simple job that should have taken less than 20 minutes on a 2013 Dodge Avenger 2.4L DOHC, took a whole lot longer…
And no the VC gasket tube seals were not leaking as you can see in the 1st picture, that was lubricant that I had sprayed down in the tubes to be able to get my pick between the rubber and the plug…
You should see what the idiot before me did to the motor mount and then no other shop would hardly touch it, Yes I fixed that also in my home garage… lol
I think the name means ‘red grease compatible with rubber’, not ‘grease made with red rubber’. Red rubber grease was originally made with vegetable oils, no rubber involved.
1 Like
Those plugs had another good 100 miles left in them 
How to take a routine job and turn it into a day long frustration fest in one simple step… or lack thereof…
2 Likes
No COP technology at my humble abode but I have had occasional difficulty removing sticking spark plug boots. Usually I can figure out a way to pry them off using a bent screwdriver, etc. But I was thinking what i really need is a slide-hammer type of tool designed to remove spark plug boots. Never seen such a tool.
There are boot removal pliers, and this:
1 Like
Silicone is fairly inert. I doubt that there would be a problem with rubber degradation. Sources I see online indicate that silicone greases and rubber are compatible.