Dielectric grease vs. thermal transfer grease

midnight sun · December 22, 2005, 06:02:15 PM

Just curious what the difference is. Am changing out my HEI ignition module and the new one came with dielectric grease. Then I read an article by an MSD Tech and it said to never use dielectric grease but to use thermal transfer grease. I've tried finding some for automotive applications but can only find stuff related to computer use.

Can anyone enlighten me?

Thanks in advance

Land Yacht · December 22, 2005, 08:05:45 PM

I cannot enlighten you as for the difference.... But I used the dielectric grease supplied with my replacement module on a stock HEI and it lasted for many years with no problems.

HOTRODSRJ · December 22, 2005, 08:11:24 PM

Dielectric grease usually is silicone based, water/moisture/corrosion resistant lubricant that protects against high voltage electrical arcing to a certain specification (usually MIL S8660). They usually are very temperature stable as well.... -40* to 450* ish! They do not have heat conducting properties per se...but will conduct heat to a certain extent.

A heatsink grease is completely different in that while they are silicone based and a good dielectric......and temperature stable...they have metal-oxide fillers (that are non conductive from an electrical standpoint) that promote heat transfer at very high rates.

I would use the heat sink grease on the module for heat transfer and I have only seen quality modules come with the heat sink grease (white paste). Radio Shack would have it.

58Apache · December 22, 2005, 08:15:51 PM

While I don't claim to know the total chemical make up of the two greases, the dielectric grease is made NOT to conduct electricity. The thermal grease ( I always knew it as heat sink compound ) is made to conduct heat, or make a better heat transfer from one metal surface to another.

In general, the metals that conduct electricity the best: copper, aluminum, silver etc. tend to also be great heat conductors. Thats why you see those metals used on the best pots and pans in the kitchen. So I suspect that there are some conductive metallic components to thermal grease.

I love using dielectric grease on electrical connections. Not for the insulating properties, but maybe in spite of it? It keeps moisture and other contaminants away from the metal to metal connection.

The only other thing I can think of is using the dielectric grease for easing the wires through rubber grommets and such. Do the instructions actually say to put the dielectric grease on the bottom of the module?

Steve

midnight sun · December 22, 2005, 08:37:21 PM

Quote from: "58Apache"Do the instructions actually say to put the dielectric grease on the bottom of the module?

Steve

Yes it does. Its a "Standard" ignition part and specifically states to put the silicone dielectric grease onto the bottom of the module. I would assume that they know what they are doing but it is still interesting that quite a few folks recommend the white grease which is also what was on the original one. I also went to a GM parts place today and he looked at me like I was stupid when I said I wanted thermal transfer grease. He said that GM used dielectric grease with their module's. When I asked him why they came originally with white grease he looked at me like he didn't believe me. I left kind of shaking my head.

enjenjo · December 22, 2005, 09:21:35 PM

If it's made for computer use, it will work on the module no problem.

midnight sun · December 22, 2005, 10:35:07 PM

Quote from: "enjenjo"If it's made for computer use, it will work on the module no problem.

OK Frank but which would you use/recommend? Dielectric grease or the thermal transfer grease (white paste)? :?

enjenjo · December 22, 2005, 11:31:37 PM

Well, if I have it, I use the thermal grease. And if I don't, I use dielectric grease. My NAPA store carries both. Although I have a buddy who packages it for just about everybody, so I normally have lots of both.

Clear answer huh?

midnight sun · December 23, 2005, 12:20:26 AM

Quote from: "enjenjo"Well, if I have it, I use the thermal grease. And if I don't, I use dielectric grease. My NAPA store carries both. Although I have a buddy who packages it for just about everybody, so I normally have lots of both.

Clear answer huh?

Yup....Clear as mud!!!! If NAPA has it, I think Ill go with the thermal grease.

Thanks for everyones input.

58Apache · December 23, 2005, 10:32:15 AM

I have worked with thermal grease during my years as an electronics technician, but also had an opportunity to work with some cryogenics where they need to transfer cold temperatures that are very low. I thought I remembered that there was a high silver content in there, and doing some research to refresh my memory I verified that the best thermal compounds do actually use microscopic particles of silver to help conduct the temperature transfer. That would be overkill for this need though I would think.

The only reason I can think of that GM would specify dielectric grease is they weren't concerned about heat transfer for some reason. Maybe the part doesn't get that warm? Maybe they want you to buy more of them? Maybe the technical manual people didn't enterpret the engineering specifications properly?

Given the use, I think I'd still use a thermal compound. Good thinking posting here to get input and help you make up your mind. Sometimes it's good to question if you're doing things the best way possible. But that's why I'm here, to get the collective knowledge to do things the best way, not just the factory way. If the factory way was always the best there might not be much of an aftermarket?

Steve

enjenjo · December 23, 2005, 07:04:29 PM

Well, Standard Ignition, Neihoff, and Echlin all supply dielectric grease with new modules. Delco and MSD come with thermal grease. Never has a problem with any of them that could be traced to the grease used.

I use dielectric grease on computer connections, plug wires, and other connections under the hood, on light wiring and sockets I use TruckLite NYK anticorrosion compound.

Silicone sealer is not a good Idea on electrical connections, a lot of it is acid and may cause corrosion. Acetic acid is what makes it set up. There are some low acid sealers out there, usually labeled sensor safe.

Bruce Dorsi · December 23, 2005, 10:06:19 PM

Quote from: "enjenjo"...on light wiring and sockets I use TruckLite NYK anticorrosion compound.

Frank, is that the red or green grease-like substance found on bulb bases?

Where can I find that stuff?

enjenjo · December 24, 2005, 12:00:45 AM

Same type of stuff. this is a reddish brown color. I get it from the local truck parts dealer, he stocks it. I'll check and see if it's in the NAPA catalog. Anyone who handles TruckLite lighting should be able to get it.

Fat Cat · December 24, 2005, 08:11:11 AM

Quote from: "Bruce Dorsi"
Quote from: "enjenjo"...on light wiring and sockets I use TruckLite NYK anticorrosion compound.

Frank, is that the red or green grease-like substance found on bulb bases?

Where can I find that stuff?

Napa Online lists these different options. You may or may not be able to get these at your local store.

8 oz container

http://www.napaonline.com/MasterPages/NOLMaster.aspx?PageId=470&LineCode=LIT&PartNumber=97940&Description=Grease+-+Dielectric+Silicone

2 oz tube

http://www.napaonline.com/MasterPages/NOLMaster.aspx?PageId=470&LineCode=LIT&PartNumber=97944&Description=Grease+-+Dielectric+Silicone

or one quart

http://www.napaonline.com/MasterPages/NOLMaster.aspx?PageId=470&LineCode=LIT&PartNumber=97943&Description=Grease+-+Dielectric+Silicone

This one is listed with the disclaimer that it can be bought at the local store and is listed as a 5 oz tube.

http://www.napaonline.com/MasterPages/NOLMaster.aspx?PageId=470&LineCode=LIT&PartNumber=98013&Description=Grease+-+Dielectric+Silicone

HOTRODSRJ · December 25, 2005, 06:12:54 PM

Quote from: "58Apache"The only reason I can think of that GM would specify dielectric grease is they weren't concerned about heat transfer for some reason. Maybe the part doesn't get that warm? Maybe they want you to buy more of them? Maybe the technical manual people didn't enterpret the engineering specifications properly?

Given the use, I think I'd still use a thermal compound. Good thinking posting here to get input and help you make up your mind. Sometimes it's good to question if you're doing things the best way possible. But that's why I'm here, to get the collective knowledge to do things the best way, not just the factory way. If the factory way was always the best there might not be much of an aftermarket?

Steve

I am with you on this one Steve. For the most part....stock HEIs with coils that are stock probably do NOT need a lot of heat sinking (simple corrosion control) becaused they are designed as such......but as you add lots of RPMs (since the frequency/rpms determines how long the coil remains saturated to the limit of the coil specifications...meaning the average current will increase thru the module) and of course fancy-smancy aftermarket coils that provide extra high spark (again...a current to voltage device ...so increase in current and therefore power)...both will require extra heat sinking to some degree.

I know...I have mixed hipo coils with cheap modules only to overheat them and eat them up and this results.....

I'm stick'in to heatsink grease since that's what it is?