Do Iridium Plugs Last Forever?

artbuc · Jan 19, 2015

A few years ago I read a Denso paper (still have it if anyone is interested) describing Denso's effort to develop an iridium plug which would last 200k miles BEFORE dropping off in performance. They presented all of the test results which showed they had accomplished their objective. I have changed out a few sets of iridium plugs at 120-150k miles and they all looked as good as new. Last night I changed out the NGK iridiums in my niece's 2007 TSX with 130k miles. I looked at them under magnification and the electrodes looked just like the new ones. It was amazing. I changed them out but I have no doubt they could have easily gone 175-200k miles.

Merkava_4 · Jan 19, 2015

The electrodes looked new, but was the gap still in spec?

AKhan87 · Jan 19, 2015

I changed NGK Iridiums on a 2012 honda civic with 180k, compared to new...they were identical in size...as far as the eye could see. They guy was still getting 36+ mpg that he always got so it would make sense they can easily last a long time, unless your engine burns oil, then there will be carbon buildup on it.

SteveSRT8 · Jan 19, 2015

I have run NGK's in fleet trucks well over 200k miles with no misfire.

As long as they don't foul they can last a LOOOOOONG time....

artbuc · Jan 19, 2015

Originally Posted By: Merkava_4
The electrodes looked new, but was the gap still in spec?

Yep, 43 thou.

WobblyElvis · Jan 19, 2015

I was going to change the iridium plugs in my 2006 ecotec, but if you guys are saying they last forever maybe I shouldn't. The engine runs fine [150,000 miles] and doesn't burn oil. Has anyone seen the gap increase in size with these plugs?

mulehead · Jan 19, 2015

Has some in a astro van for over 250k with out problem or wear

AKhan87 · Jan 19, 2015

Originally Posted By: WobblyElvis
I was going to change the iridium plugs in my 2006 ecotec, but if you guys are saying they last forever maybe I shouldn't. The engine runs fine [150,000 miles] and doesn't burn oil. Has anyone seen the gap increase in size with these plugs?

to be sure, measure to see how it compares to factory gap (Do not attempt to change the gap size). If in spec and not full of carbon, keep on using.

Eddie · Jan 19, 2015

Do they weld themselves to the head with so many miles and are impossible to remove?

artbuc · Jan 19, 2015

Originally Posted By: Eddie
Do they weld themselves to the head with so many miles and are impossible to remove?

Yes! That is why I always remove them at 100k and add anti-seize.

SwampSurvivor · Jan 19, 2015

I replaced the factory Iridiums on the Focus at 35 or 36K. They were still well within spec'd gap and looked fine, but there was a definite increase (or restoration) of performance and fuel economy.

sciphi · Jan 19, 2015

Depends on the plug and engine. Some engines with some plugs can go a very long time, while others won't. The plugs that have gone the farthest have been on MPFI naturally aspirated engines with fairly low output. Add direct injection or a turbo into things, and it appears that iridium plugs have a reduced, if still fairly long, lifespan.

doublebase · Jan 19, 2015

Originally Posted By: Eddie
Do they weld themselves to the head with so many miles and are impossible to remove?

This is why I think I may change mine at 100k, even though the thing is running great at 87k. I just don't want to run into problems and I have to replace 8 of them...more money and more problems.

OneEyeJack · Jan 19, 2015

The plugs in my 03 V8 4Runner looked like new when I changed them out at 100K miles. I thought about leaving them in but decided to change them anyhow. I looked inside the combustion chambers with a borescope and everything looked like brand new, all shiny and clean. If this is what I get from a computer controlled fuel system and synthetic oil then spending the extra on oil appears to be a good deal.

KrisZ · Jan 19, 2015

Nothing lasts forever, but some things do last a long time.

Pontual · Jan 19, 2015

I've used iridium 8eix in a carbed ZX9r bike and they got ruined in 15k miles. All carboned (fuel rich) ... Is there a way to clean it up, like with a torch or a fscleaner?

Corvette Owner · Jan 19, 2015

I changed them out on my daughter's Chevy Malibu at 110,000 miles and I never saw used plugs look so good. They looked brand new!

berniedd · Jan 19, 2015

Originally Posted By: Pontual
I've used iridium 8eix in a carbed ZX9r bike and they got ruined in 15k miles. All carboned (fuel rich) ... Is there a way to clean it up, like with a torch or a fscleaner?

I poured lacquer thinner into my plug's end and waited an hour till the liquid evaporated. It made the carbon brittle, which I could pick off with a needle.

Chris Meutsch · Jan 19, 2015

Originally Posted By: artbuc
Originally Posted By: Eddie
Do they weld themselves to the head with so many miles and are impossible to remove?

Yes! That is why I always remove them at 100k and add anti-seize.

+1

HerrStig · Jan 19, 2015

Originally Posted By: artbuc
Originally Posted By: Eddie
Do they weld themselves to the head with so many miles and are impossible to remove?

Yes! That is why I always remove them at 100k and add anti-seize.
+1, despite their claims about a miracle plating.

Do Iridium Plugs Last Forever?

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