I had a plug stick in my wifes car a while back, I sprayed the plug very good with Kroil penetrating oil, then let the car idle for about 15 minutes to get it good and warm with the oil around it. The following day after the engine was cooled back down the plug came out pretty easy. Anti seize the new ones for sure as you put them back in.
And then there's this.....
Lycoming, who has been making aluminum heads for around 80 years, says to remove a stuck spark plug:
1) Warm engine.
2) Use an inverted funnel - small side around the spark plug - aim a co2 fire extinguisher at the plug. The inverted funnel keeps the co2 off the head itself.
3) Let fly the co2!
4) Unscrew plug.
There's also a product called Loctite Freeze & Release that's very effective at loosening stuck plugs...
http://www.henkelna.com/industrial/p...=8797940809729
As for the anti-seize.... From the Permatex website:
Permatex Copper Anti-Seize Lubricant
A premium quality copper anti-seize and thread lubricant that may be used to prevent seizing, corrosion and galling where high temperature conditions exist. Contains a high percentage of micro-fine copper flakes in a semi-synthetic grease carrier and is fortified with high quality rust and corrosion inhibitors. Temperature range: -30°F to 1800°F (-34°C to 982°C). Provides good electrical conductivity. Meets Mil Spec #907E.
Suggested Applications: Spark plug threads installed in aluminum, exhaust manifold bolts, engine bolts, oxygen sensors, knock sensors, thermostat housing bolts, fuel filter fittings, and battery cable connections