Dielectric Grease for spark plugs

[gathermewool]

dielectric grease will not cut down on the flow of current on an electrical connection. The metal-to-metal contacts literally scrape away the dielectric along the normal contact path. The dielectric keeps moisture out to preclude corrosion.

Putting dielectric on the insulator is for lubrication.

I'm against anti-seize on the threads. If you can't help yourself, make sure to add VERY LITTLE!

 

[yonyon]

Originally Posted By: Kiwi_ME
No discussion needed - it isn't going to make a beans worth of difference.


Usually it won't make any difference. Sometimes in the real world water can end up in unexpected places. You may be safe from this on your fancy little desert island paradise, but some folk live in places that have water. A little silicone grease on the terminal nut can be that extra third line of defense against corrosion caused by water intrusion.

If you know that you don't need it then there's no sense in wasting those 10 seconds when installing new plugs. I park 12 feet from saltwater. Roadway flooding sometimes reaches over 3 feet here. I don't get to take a day off from work because it's raining.

 

[Texan4Life]

Originally Posted By: gathermewool
dielectric grease will not cut down on the flow of current on an electrical connection. The metal-to-metal contacts literally scrape away the dielectric along the normal contact path. The dielectric keeps moisture out to preclude corrosion.


+1

on CPU's that are cooled below ambient temp it is standard to slather dielectric grease on the processor pins and into the socket to prevent moisture from forming and shorting out the pins.

I'm not an expert, but if any application would be sensitive to impeded electricity flow it would be a CPU.

 

[Scott_Tucker]

As a professional mechanic, I have seen many engines that misfired because the previous mechanic smeared grease all over the terminals. It does not prevent corrosion on the metal so there is no reason to do it. I use a little on the inside of the spark plug boot to keep out moisture and aid in removal.

 

[gathermewool]

Originally Posted By: Scott_Tucker
As a professional mechanic, I have seen many engines that misfired because the previous mechanic smeared grease all over the terminals. It does not prevent corrosion on the metal so there is no reason to do it. I use a little on the inside of the spark plug boot to keep out moisture and aid in removal.


+1 The same goes for any electrical connection (in certain scenarios,) because adding too much prevents obtaining a good contact, especially on older coil-pack-type ignition system, IME. The grease will take up all of the space within the boot and push the wire contact up into the boot instead of allowing it to 'click' over the plug end.

I actually experienced this with my old '97 Legacy, and it was my fault! When I first purchased the car I did some routine maintenance, including checking the plugs and checking the wire and coil pack resistances. The previous owner hadn't used any grease, so the wire boots were stuck on the plug to the point where the wire was ruined trying to get it off. Thinking more was better, I filled the boot with grease and put everything back together. The car would throw a misfire code, which continued until I pulled the wires, cleaned out most of the grease with a q-tip and re-installed the wires. The grease, as mentioned above, was pushing the contact up into the boot, allowing for a very bad connection. A pressure was being created inside the boot, too, because no air was able to escape, since there was so much grease. This was probably causing the boot to want to slide back off of the insulator.

 

[Bamaro]

Originally Posted By: Kiwi_ME
How does it hurt the terminal nut?

Since it is non conducting I keep it away from there.

 

[Vikas]

For many years, I never understood why battery terminals were coated in grease. Eventually, light bulb went on!

Grease occupies space which might otherwise be occupied by air/moisture. This starts corrosion. Once it starts, it spreads to the actual contact area. Smothering in grease prevents the corrosion from happening and maintains the contact from erosion.

Now, if you use really fancy lubricant which has extremely high surface tension which can overcome clamping force of the battery clamp (anybody wants to run the numbers for me?) i.e. it will seep in and prevent the metal to metal contact e.g. connecting rod and bearing caps ... With the cable tight on the battery post, I do not think that is a possibility at all.

But I understand where your reluctance is coming from. I used to think the same way in the past. For example, just take two wires, take off the insulation at the ends, hook it up to multimeter and just lay the ends on top of each other. You will have connectivity or fiddle with laying on part until you do. Now put some drops of oil at the junction and watch loss of connectivity!

The problem with the above experiment is that you better NOT have any contacts where two ends are just lying on top of each other. If this is what you had to begin with, you have already lost the battle.

- Vikas

 

[gathermewool]

Originally Posted By: Bamaro
Originally Posted By: Kiwi_ME
How does it hurt the terminal nut?

Since it is non conducting I keep it away from there.


Dip both leads of a multimeter in dielectric and then touch them together to read the resistance. Is there more resistance?

 

[[RT] ProjUltraZ]

smash em together to displace the grease! they should call it non-electric grease, that might help. even on the batteries, i don't let grease get on the contacts, just all around it

 

[Kiwi_ME]

The purpose of the silicone dielectric grease on the insulator is to eliminate air between the insulator and the plug boot, as such to raise the dielectric rating to suit higher breakdown voltages needed for modern larger plug gaps and higher combustion pressures. Only a very small amount is needed.

Silicone dielectric grease also works well to preclude moisture (and potential corrosion) within the contact area of just about any spring-forced electrical contact, which is just about everything. It's especially effective when extremely low currents and/or dissimilar metals are present.

 

[gathermewool]

Originally Posted By: [RT
ProjUltraZ]smash em together to displace the grease! they should call it non-electric grease, that might help. even on the batteries, i don't let grease get on the contacts, just all around it


Not sure if this was in response to my multimeter-leads-dipped-in-dielectic, but if it was:

No need to smash anything together. There will be no change in resistance; what is measured for lead resistances will remain the same. I probably should have stated that instead of being cryptic.

To Kiwi_ME's point, this is why it's especially good to use dielectric for connections in areas prone to accelerated corrosion, such as marine applications. A little bit of dielectric on your fish-finder's connector goes a long way toward preventing corrosion and the associated connection issues.

 

[InvalidUserID]

DOH! I knew I was forgetting something. Did my plugs a few weeks back.

I usually just buy one of those .99 cent packets and put a little bit inside of each wire boot. One packet should be enough for one job, maybe even have a little left over.

 

[xBa380]

I just replaced my plugs an hour ago in my 2008 Scion xB... The factory plugs were Denso Iridiums (replaced with NGK equivalents).

I ended up smearing a light coat on the porcelain on the outside of the plug and at the end of the boot before replacing them on the new plugs. Car started fine with no codes or issues, so that is a good sign

I checked the gaps of the OEM plugs and 2 were right where they needed to be, one was slightly out and one was quite a bit out (wider gap). What kind of effects would this of had on my car? I have noticed fuel economy is lower then when I bought the car, even with lighter wheels/tires and such. I read wider gaps can reduce fuel economy and such, so I wonder if that is what my issue was. Of if it would be so slight it would make no difference at all?

I was quite surprised on the wear though of the one plug, especially considering I am only at 68K and these plugs are rated at 100-120K or whatever.

 

[DGXR]

I take a dab "size of a piece of rice" and put it on the end of a small flat blade screwdriver and smear it around the inside of the boots. It works great. If you use more it's just a waste and will just be pushed out of the way. This seals the boot/terminal from moisture/water intrusion.

This, just a small amount smeared around inside the spark plug boot. The grease also helps to prevent the rubber boot from bonding to the ceramic insulator over 10+ years of heat cycles.

 

[TCL]

This, just a small amount smeared around inside the spark plug boot. The grease also helps to prevent the rubber boot from bonding to the ceramic insulator over 10+ years of heat cycles.

This^^^^^^^

 

[sk_pete]

silicone oil can also withstand high voltages and does not hurt rubber.
any reason to pick one over another ?

 

[mattd]

This, just a small amount smeared around inside the spark plug boot. The grease also helps to prevent the rubber boot from bonding to the ceramic insulator over 10+ years of heat cycles.

you dug up a 9 year old thread for that?

 

[mfewtrail]

you dug up a 9 year old thread for that?

He didn't actually bring this back up. Yesterday when I viewed this thread, it was back to the top because of a post by a new user that was possibly a spammer, bot, or advertiser.