Copper anti-seize on spark plugs

The danger is some careless mechanic slobbering it on the INSULATOR, which WILL create misfire.
A thin even coat on the threads is good practice.

Why stop there?? I use the Permatex silver on the exhaust nuts too. Seriously, anti seize can only benefit any threaded connection with no downside.

Additional useless info:
I think the only motorcycle I've owned that I have used anti-seize on the plugs is the old Norton. Doesn't hurt a thing. Doesn't need it, but I like using it anyway. It just feels so good screwing the plug in there.

The label on the 35-year-old tube of Silver colored anti-seize I have a little left of says it is good to 2000F. The copper-colored stuff I bought recently within the last 3 years isn't rated on the label. I also doubt it has any copper in it.

I've have not used a torque wrench on a spark plug in 71 years, but I have said torque down the plugs. Obviously, I have a severe case of brain fog.

concours said:

The danger is some careless mechanic slobbering it on the INSULATOR, which WILL create misfire.
A thin even coat on the threads is good practice.

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Agreed. I was taught to use it sparingly and to coat all but the first thread [closest to the business end]. General rule of thumb. Any fastener where the torque value is quoted as "dry", reduce the torque value by 10% when using any sort of lubrication. If you ever do get NeverSeize on the porcelain, use aerosol brake parts cleaner & compressed air to remove it. Both silver and copper color NeverSeize are conductive and will short out the plug if it gets on the porcelain.

For the gland bolts which hold the exhaust pipes onto the cylinder head, tighter is better, so use NeverSeize! I have a collection of HeliCoil tools. I can tell you that I paid well over $100 US, 20 years ago for the 14mm spark plug HeliCoil set. I've seen plenty of seized bolts & spark plugs. Usually caused by a Back Yard Bob. If a fastener is installed into aluminum long enough, the cadmium or zinc plating will be sacrificed. Once you have bare iron or steel against aluminum, you have created a weak battery. Google "galvanic corrosion" if you want to know more. Brass [not bronze] against aluminum is even worse.

I've never used a torque wrench on a spark plug.

I use silver Permatex anti-sieze because I still have a half empty tube which seems to last for half a lifetime. It does tend to burn off within a short amount of run time. Next time, I will look for something with a higher heat rating.

FWIW, In the "old days" many brands of spark plugs had no protective coating of nickel (or whatever) and we always used antisieze on them. Most (all?) modern plugs are designed to work with AL heads and have a coating that eliminates the need for anti-S and we never used it on those spark plugs when engine building.

The primary cause of seized plugs is over tightening. For plugs with gaskets it is only necessary to turn them in until they bottom and then give them another 1/2 turn. It certainly doesn't hurt to use anti-S as long as some attention is paid to using a very small amount and not over tightening the plug/stripping AL cylinder head threads due to the added lubrication.

Finger tight until they bottom + 1/2 turn with the plug wrench eliminates any concern re tightening regardless of whether antisieze is used or not.

Rinse repeat

I think the consensus here is there ain't no consensus

Only thing I'd add is to be cautious if using a thread lube on the cylinder head bolts as they seem to be near the yield limits at the spec'd torque amount. As has been mentioned, lube means more tension will be generated on the material at the same torque value, so gotta dial down the click point on the wrench (10%??).

From what I recall from years ago seeing a list of torque differences between various lubricants, the least amount of torque change was 20% and some lubricants were 50%+! Keep in mind that almost anything you put on threads, whether it be what we usually think of as a lubricant or things like thread lockers, is a "lubricant" as far as the fittings are concerned when tightening.

MexicoMike said:

From what I recall from years ago seeing a list of torque differences between various lubricants, the least amount of torque change was 20% and some lubricants were 50%+! Keep in mind that almost anything you put on threads, whether it be what we usually think of as a lubricant or things like thread lockers, is a "lubricant" as far as the fittings are concerned when tightening.

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I copied this from this site a little while ago.

Dommie Nator said:

I copied this from this site a little while ago.

View attachment 85189

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That's quite significant. Makes me shiver to think about a slight oil contamination on things like headbolts, unbeknownst to the owner as he innocently torques to spec! The 3/8" studs spec'd for 30 ft-lbs...and Mr. Comstock shows them pulling at 40-45 ft-lbs.

The torque coefficient on the CRC Nickle anti-seize I got from the auto parts store is 0.15