Nissan Repair: Cant remove seized spark plugs, aluminum paste, nissan quest

Question
2001 Nissan Quest Mini Van..Recently purchased ... Unab le to remove seized or stuck spark plugs.. Mechanic twice has put lubricant whatever they use to try a loosen it but nothing helps... Doesn't budge.. Won't force it fearing it will break...

Would a nissan dealer have better luck removing them????????
Please offer any suggestions...

Answer
Bob,

If the lubricating oil will not loosen the plug where you can get it out I would make plans to be down for a while.  If the plug damages the threads on the way out you are looking at removing the head to get the threads renewed.  Second, be sure to try doing the plugs when the engine is cold.  Aluminum expands twice as much as steel when it heats and that is another reason the plugs would be difficult to get out.  Liquid wrench is a good lubricant and is what I use for such issues.  Also, go to a larger socket and breaker bar to get better leverage.  I know it is not recommend but I have used an impact in some instances to break it loose.  Galvonics where the metal has almost become one at the point of contact (threads) makes it difficult to get the plugs out.  That being said use an aluminum paste on the threads of the new plugs to preclude this from happening again.