Poor heat transfer could lead to damage to the plug as it will go passed the critical self-cleaning temp, to hotter than it should. It may crack the plug or it may wear out fast. Sound right anybody?
This much I do know......
Zetec - Aluminum head, Cast Iron Block
Duratec - All Aluminum heads and Block w/ steel cylinder sleeves
Well, I used anti-seize on my +4's with no problem. Mind you, I first applied the anti-seize, then wiped with a dry cloth to get most of it off. That leaves so small an amount, only that which is required to prevent corrosion, left behind. I was also told by a dealer and part time rally car mechanic for Team Subaru that if you do use anti-seize, use VERY LITTLE and use the bronze coloured stuff. Holds up better in the heat.
Just my .02 worth
Hope that helps.
