Used Plugs ?

[RickMar]

I was stumbling around a junk yard yesterday and I saw a Mounty with a 5.0L engine. I looked through the wheel well and everything looked new. Just for the heck of it I pulled a spark plug...excellent condition!! I pulled the other 7 plugs all in the same condition. I was looking through my service manual DVD to double check the GAP.. Then I saw a strange notation :
Make sure to place the used plug back into the same cylinder from which it was removed. New plugs can go into any cylinder.

I am sitting here trying to figure out the logic of the notation pertaining to used plugs being place back to the same cylinder. The used plug is not going to shrink, turn from Platinum to Gold, or not work because it does not like the new neighborhood etc, etc. Can anyone fill me in on what I am missing ? A plug is a plug is a plug new or used right?
Any info will be appreciated.
Thank you,
Rick

 

[imp]

.... Can anyone fill me in on what I am missing ? A plug is a plug is a plug new or used right?
Any info will be appreciated.
Thank you,
Rick

You aren't really missing anything. It's just generally accepted nowadays that each part removed should go back where it was. Important consideration for things like pistons, valves, lifters, etc.

Realistically, each cylinder experiences slightly varying conditions from the others, and therefore the plugs may reflect those differences in the way they are consumed, deposit build-up, etc. So, maybe a plug placed in another cylinder MIGHT experience hot-spots in would not in it's original cyl., and cause pre-ignition.....

Enough balderdash for tonight, now. imp

 

[RickMar]

Thank you IMP for the information. it now makes sense.
Rick

 

[waskly]

Make sure to place the used plug back into the same cylinder from which it was removed. New plugs can go into any cylinder.

I am sitting here trying to figure out the logic of the notation pertaining to used plugs being place back to the same cylinder. The used plug is not going to shrink, turn from Platinum to Gold, or not work because it does not like the new neighborhood etc, etc. Can anyone fill me in on what I am missing ? A plug is a plug is a plug new or used right?
Any info will be appreciated.
Thank you,
Rick

this only applies to factory plugs.

since the car comes off the line, factory plugs are matched to banks.