lubricate before removing spark plugs?

[AC Mech]

I want to inspect my plugs as they have been in for 5 plus yrs, and I am concerned about breaking a plug off in the head. Is it ok to use some penetrating oil to make the removal easier?

Also the plugs have maybe 12k on them, do they need to be changed? The car runs great.

 

[Rich'sTRsvt]

Not sure about the oil, but it is safest to do it when the engine is cold with aluminum heads so as not to take the threads with the plug.

 

[jblood37]

I used a little wd-40. I let it do it's work for 24-48 hours and then removed.

 

[FiveOhJoe]

The penetrating oil will probably never even reach the threads because it seals at the shoulder above the threads

 

[oldmodman]

Back the plug out half a turn. Spray carb cleaner down into the plug hole.
Wait half an hour. Turn the plug down the half turn again then back it out slowly. If you feel it start to bind up at any point. Stop. Turn it back down half a turn and spray more carb cleaner into the hole. Start removing again.
A lot of problems in removing a plug can be caused by the hard ring of carbon at the end of the threaded area getting up in the threads and binding everything up.

This process isn't that critical with the four valve heads but it's very important on the three valve ones. But after seeing a threaded end broken off in an engine I use this method when I am removing any high mileage plugs. In anything. if you change your plugs quite often, like every few thousand miles, you shouldn't need to worry about carbon build up on the end of the plug. It's mostly a problem if the plugs have been in the head for more than 50K.