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I think A/C Delco says the same thing. Plugs are nickle plated if I recall correctly.
The NGK trivalent Zinc-chromate coating on the threads provides both the desirable anti-sieze properties and corrosion protection from dissimilar metals (aluminum head and steel spark plug). Also, their coating probably provide a good (low impedance) electrical bonding path across the thread interface, as well as between the plug body to crush washer and head.
Spark plug threads get exposed to combustion gases as well as the dis-similar metal issues. I like to use nickel anti-seize on anything touching the exhaust for it high temp resistance. Like others have said, there is no downside to using it so why not.
After having a Champion seize up and ruin some threads, I always use anti-seize, and use NGK spark plugs
I use antisieze on ANY item I for sure and may remove at a later date. Plugs, lugnuts, carb studs in manifolds, exhaust fasteners etc etc.
When it comes to spark plugs in our type vehicle I always use anti seize, I never use a torque wrench, there's no freaking room to use a torque wrench correctly. I tightened them until the Crush Washer it's crushed and then give a little bit more that's it I will check them in a couple hundred miles I'll check them and see if anything moves. Spinning wrenches for a living you get to know when enough's enough. Or you just cost yourself time and money.
I've never needed to add anti-seize on any plug on any aluminum headed headed motor ever, on any brand car or any motorcycle... it's just not needed IMO, but hey, cover yourself head to toe in silver anti-seize until you look like the Tin Man in The Wizard of Oz... hehe. And torquing a plug is just not needed either, you tighten the plug, feel the crush washer compress, and then stop.. that's it. The only way a plug is ever going to seize in an alum head is if you massively over tighten the crap out of them which only a gorilla would ever do (no offense to gorillas), or if it's a one of those Satan-engineered long ass Motorcraft plugs in the Ford Triton truck engines... but don't think we're talking Ford here so... ha (in that case, I don't care how much anti-seize you add, it'll still seize and break off the next time you try to remove them).
In my case it was brand new B1 heads and the Champion spark plug. Just screwed in finger tight (no tool at all) on the work bench to check the plug reach and protrusion into the chamber. I was removing it with my fingers and when it was almost out the last few threads cold welded the aluminum threads to the steel plug. I think just a bit of oil may have prevented the problem, but the damage was done and I learned my lesson not to install the plugs dry.
Copper anti seize is not to be used with aluminium something to do with electrolysis of dissimilar metals from what I remember. Not quite sure on that. I have never seen the problem but stopped using it just in case. If any materials are going to gall threads it is stainless steel or aluminium. Like others have said a little dab of nickel anti seize cannot hurt.
A little dab of "I'm a tin man" and fresh soft copper crush washers with every install. It serves two purposes. 1- it keeps the metal plug from seizing and ruining a $$$$ aluminum cylinder head and 2 - it works as a heat sink paste to keep your plug and cylinder temps uniform with each other.