On Thu, 18 Dec 2014 18:26:51 +0000 (UTC), "Danny D."
wrote:

Stormin Mormon wrote, on Thu, 18 Dec 2014 08:30:05 -0500:

Some times when they won't release, twisting the
spark plug boot will help break them free.

Rest assured I twisted and twisted. You can't get even
180 degrees though, due to the very short high-tension
wire, so, it's a situation where you're limited.

Given that the metal-to-metal connection is circular,
and that both metals are nearly pristine showing no
signs of corrosion whatsoever, I think it was just
stuck on tightly, metal to metal.

I think the "never sieze" on the threads is excellent
idea. I always grease or neversieze mine on lawn mowers,
etc.

There are two schools of thought on the never seize.
One school of thought is that it prevents corrosion (by
being the sacrificial anode), while the other school of
thought is that careless people will overtorque and even
more careless people will end up shorting out the electrode
due to the excess of never seize squeezing into the cylinder
itself.

Knowing all that, I'm careful when I use it.
I generally put on just enough to colour the threads on one side.