Replacing Old Plugs in an Aluminum Head Pathfinder

Perhaps this is a dumb question for a hopefully simple task, and maybe I'm overthinking this, but I'm more than a little concerned about replacing the plugs in our 2008 115K mile V8 Pathfinder.  I was originally resigned to taking it in for plugs, but I'm not sure I trust a shop more than myself who has all the time I need to do it right.  Here's the current plan:

• Blow out any debris with compressed air
• Saturate the plug with PB Blaster
• SLOWLY and by hand back the plug out
• Put in new NGKs (I think this is Nissan OEM) without anti-seize since NGK claims their plugs are plated so they don't need it.  (is it safe to buy these from Rock or should I look elsewhere?)
• Drive away happy...

Any advice appreciated.  These things have been in for about 16 years and 115k miles.

I've never had an iron head engine and I never worried that much about changing plugs. Unless there's a known flaw with the plug threads on this engine you're probably overthinking it. Just blow out debris, remove by hand, carefully thread back in by hand to avoid crossthreading.

@GameboyRMH, thanks, I hope so.  I've also never let plugs go this long so I'm not sure what to expect.  Guess we'll see.

as an aside - damn, plugs have gotten expensive.

Make sure the block is cold.  Hot heads can mess up threads when removing? - I have a thread chaser I had to use in my '85 200SX.  Maybe that's not a thing anymore?

In reply to jwagner (Forum Supporter) :

I think the value-for-money of plugs is actually increasing, if you install iridium or ruthenium plugs you can probably forget about them as maintenance items and just change them with engine rebuilds.

Any preference on iridium or ruthenium?  They're about the same price on Rock.

I would just use whatever OE is. Modern ignition systems tend to be designed around a particular plug type and stuff can get weird when you deviate.

Also, second the "you'll probably be fine". A couple years back I did the plugs for the first time on a 126k 2006 Miata (OE Iridium plugs) without really thinking about it or doing any special prep and everything went smoothly.

If anything causes threads to gall, it's carbon stuck on the business end of the spark plug.  No amount of penetrating oil or other magic potions is going to do anything for that.  There's a really nice pressure tight seal that makes this impossible.

Just treat it normally, spark plugs galling is really rare nowadays.  I've never had it happen.

Now if you want scary, an old Porsche guy told us that he always removed air cooled Porsche plugs with a hot engine and an impact gun.

In reply to Pete. (l33t FS) :

That's a scary thought.

I've had snowmobile plugs come out with the threads when changing fouled ones in the trail, but only with a not engine, never had issues when cold. Not a fun thing to have happen out in the woods.

I can see the Porsche guys point at least.  The aluminum may be softer but it's also expanded with heat.

He said he did it that way because he had more problems with cold engines.  Well, it's HIS ass on the line, his shop, he can do what he feels is most prudent.

My last few cars have all had 100k plug intervals, and none of them have given me trouble.  Starting with a cold engine, using the OEM recommended plug, a dot of antiseize out of habit, and a little patience has always worked out. 

Putting wonder metal plug in and forgetting about them is a great way to damage threads later. As Pete mentioned, it's the buildup on the plugs that causes problems. 

I make a habit of loosening and re-torquing plugs every couple of oil changes if my engine has an absurdly long plug change interval. Just to be sure I can actually get them out later.

jwagner (Forum Supporter) said:

Any preference on iridium or ruthenium?  They're about the same price on Rock.

Ruthenium's supposed to last longer but as ShawnG mentioned there can be downsides to leaving plugs in for very long periods unnecessarily, so unless it's an engine with totally unreachable plugs you should avoid running them until they malfunction.

In reply to GameboyRMH :

Not just for thread life.  The way ignition coils work, when the power is turned off and the magnetic field in the primary collapses, the induced voltage in the secondary builds up until it gets high enough to make the spark.  A worn plug needs more voltage to jump the gap.  This breaks down the coils faster and causes them to fail.  Failing coils usually coincides with using spark plugs well past their sell by date.

This was a major reason why GMs used to eat coil packs on DIS cars.  Bad wires, worn plugs, it would just cook those double ended coils that really were too large to deserve having issues.

The other thing is, that 100k interval or whatever (some newer engines are 30k or 60k) is a maximum life... there's nothing wrong with changing them early.  And if a coil fails before the spark plugs are "due", replace all of the spark plugs and probably all of the coils too...  those coils are like catalytic converters in that they don't die, they get killed.