Iridium worth it over Ruthenium?

[QwikKota]

These are some Iridium plugs with 105k miles on them, for reference. AC Delco 12627160. Replaced with NGK 4344. I did not check the gap but 2 looked similar to the new plugs and 2 looked worn down (#1 and #4). No noticeable difference in performance but the 4 cylinder Colorado is not exactly a sports car.

 

[thastinger]

There was a time not long ago when plugs were changed at 5k, and now you're complaining at 100k....

Yeah, but you didn't have to pull the cab off a Model T to change the plugs.

 

[martinq]

These are some Iridium plugs with 105k miles on them, for reference. AC Delco 12627160. Replaced with NGK 4344. I did not check the gap but 2 looked similar to the new plugs and 2 looked worn down (#1 and #4). No noticeable difference in performance ...

One of these plugs is not like the others. I think I can see which cylinder is burning oil.

 

[QwikKota]

One of these plugs is not like the others. I think I can see which cylinder is burning oil.

Someone on the Colorado forum suggest that one cylinder (#3) has a clogged injector. This is a DI engine. No smoke out of the tailpipe.

 

[jkittlesen]

Has anyone posted the spark plug test video from Torque Test? Seems that counterfeit plugs are everywhere:

Torque Test Channel
Mar 13, 2026
We Tested $500 in Spark Plugs, 33% were Counterfeit

Thank you for the video post.

 

[Snagglefoot]

These are some Iridium plugs with 105k miles on them, for reference. AC Delco 12627160. Replaced with NGK 4344. I did not check the gap but 2 looked similar to the new plugs and 2 looked worn down (#1 and #4). No noticeable difference in performance but the 4 cylinder Colorado is not exactly a sports car.

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I believe the quick AC Delco reference 41-115.

 

[Snagglefoot]

The front bank is easy peasy. The rear bank requires wobble extensions, extensions of various sizes and spark plug sockets that have foam or grabby stuff. Masking tape and duct tape and a mirror on an extension wand don’t hurt, and a stable step stool helps. If your chest is not on the engine, you’re not doing it right. All that said, it is by no means impossible. It is harder than it should be.

I call it the “ Flying Superman” stance.

 

[Snagglefoot]

I haven’t seen the term “ Double Iridium “ used, at least at Rock Auto. They do use the term “ Double Platinum” I have been using AC Delco and for the last 18 years they are what you would call “Double Iridiums. Here are pics from three different plugs the first two shots were in a 6.0 Chevy for an amazing 180,000 miles.

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The next two shots are for an AC Delco 110 that went into the engine in 2018. It is also a “ Double Iridium.

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They are going to be pulled this summer at about 290,000 mile and this new set of 165’s is doing in. This is Chevy’s newest design for Gen IV engines. Notice the “collar” at the base of the electrode. It too would be considered a “ Double Iridium.

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I typed 165. They are actually 162 as in the pic.

 

[Snagglefoot]

As for the $2.00 copper plugs, just use them if you want something to do, otherwise hike your suspenders and put in Iridiums.

 

[QwikKota]

I just had to buy 16 Iridiums for my Ram. Hopefully the Rock Auto parts are legit. Nearly $125 for the plugs. Very expensive.

 

[f355spider]

All iridium gets you is a somewhat increased change interval. The only reason they switched to ruthenium was the high cost of iridium. That’s it.

Not all Iridium are necessarily longer life. I found out within the NGK lines, they make at least two grades of Iridium and Platinum spark plugs. The difference in them is the longevity and tip design. Their IX version is considered the premium, higher performing version. It have a finer tip than the OEM Laser Iridium plugs...and the IX cost less. I called NGK to explain better the difference in price and the technician said the OEM versions cost more because they have slightly thicker Iridium in the tips that allow for close to double the life. He said the IX may only last 40k to 50k miles, while the OEM Laser Iridium are designed for 80k to 100k life.

Not sure if they are still made, but there were similar difference he explained about their EIX Platinum versus their OEM Laser Platinum plugs.

 

[f355spider]

When it comes to spark plugs use what the oem originally used

That is exactly what I have done for the past 20+ years.

 

[tbm5690]

Just replaced the factory NGK laser iridium plugs with NGK ruthenium. 104k miles. All 6 plugs are in great shape, look the same and have identical gaps. I've had VCM disabled since 74k, whether or not that matters. I was somewhat expecting the rear bank plugs to look a bit different from the front. First pic is front bank, then back bank, then the final pic comparing the new plug to the old. The total length is shorter, despite the threads being the same. I suppose this means the electrode on the new plug will be more recessed in the cylinder. I assume no concerns there...would you all agree? Oh...and what a piece of cake despite being a transverse V6. Not sure if a J35 plug change would be any harder on something like an Accord or ILX with less space, but the last couple of times I did plugs on a transverse 6 was my Lexus with the 3MZ-FE and a Mazda with the Duratec V6...brutal in comparison. Dare I say I actually enjoyed this job.

 

[Urshurak776]

I know my thought may not apply to this situation and I do understand and have used high end spark plugs in my modern supercharged and turbo engines but 20+ years ago with the purchase of a Harley that the plugs were super easy to get at and remove I decided to try every plug available over a period of about 2 years, as more of a test to find the best plug for the bike.

Say what you will about a Harley being old tech but riding on top of a engine with wheels and knowing the bike well the slightest change I could feel via my "Butt Dyno".unlike in a car. Platinum, Iridium, E3 etc, I settled on the best running, best butt dyno, best EZ starting plug and that plug was the basic Copper AUTOLITE $5.99 taking the WIN!

In that old bike I can change the plugs in 2 min, so long lasting 100K mile plugs was NOT the goal, best running was.
I know old school copper won't last long but I ask is copper ( least resistance ) the best way to pass electrons and get a spark be it only a few thousand miles? I wonder but I guess my point is I will always question spending crazy amounts on spark plugs.

Personally I treat plugs like my oil changes. I don't try to get hyper miles on a oil change using $$$ boutique oil. I use normal oil but simply change it often.

I once purchased used Police cars at auction and got to know the guys at the shop that maintained 150+ fleet of Police Vics, I will never forget the County garage manager telling me he once had a fleet wide issue of coil packs going out on the Crown Vic, He went from 100K to 60K plug changes and his failed coil pack issue went away.

He also said the Crown Vic was the best Police Car ever made!

As far as relating to this thread, I ask do these longest lasting 100K+ mile Precious metal plugs that last so long have a trade off to get that kinda high miles on a plug? I would be worried a plug would simply get stuck leaving in in an engine so long...
I will never un-hear what that guy told me about his coil packs going bad so 60K max is what I try and do. why not?

My Harley Sportster got Champion Plugs (Copper) every year. They, at the time, made the OEM plugs for my Sportster (at 8.3 million times the price because it says "HD" on them.) I just bought a 4 pack every two years from the local parts store. Probably $2 a plug. Put in a new set every Spring. I only put 3-4K on the bike every year, so could have probably just changed them every 5 years and been fine.....even with copper.

 

[Snagglefoot]

Not all Iridium are necessarily longer life. I found out within the NGK lines, they make at least two grades of Iridium and Platinum spark plugs. The difference in them is the longevity and tip design. Their IX version is considered the premium, higher performing version. It have a finer tip than the OEM Laser Iridium plugs...and the IX cost less. I called NGK to explain better the difference in price and the technician said the OEM versions cost more because they have slightly thicker Iridium in the tips that allow for close to double the life. He said the IX may only last 40k to 50k miles, while the OEM Laser Iridium are designed for 80k to 100k life.

Not sure if they are still made, but there were similar difference he explained about their EIX Platinum versus their OEM Laser Platinum plugs.

Another difference between the IX and the Laser Iridium is the small disc of either iridium or some other erosion resistant material on the ground electrode of the Laser Iridium. I have a set of IX plugs in a V-6 with a waste spark design. I expect the front bank will wear out in those 40-50 thousand miles.

On the other hand I had a set of original AC Delco “ double Iridiums “ last 180,000 miles, and the second set lasted 110,000 miles and were still decent after I pulled them. The engine is 6.0 LS with 290,000 miles with a third set of AC Delco double Iridiums installed. The third set has a slightly thicker Iridium tip with a “collar” at the base. Both the AC Delco and NGK “ double Iridiums” have the same design with the “collar”.

 

[Snagglefoot]

Just replaced the factory NGK laser iridium plugs with NGK ruthenium. 104k miles. All 6 plugs are in great shape, look the same and have identical gaps. I've had VCM disabled since 74k, whether or not that matters. I was somewhat expecting the rear bank plugs to look a bit different from the front. First pic is front bank, then back bank, then the final pic comparing the new plug to the old. The total length is shorter, despite the threads being the same. I suppose this means the electrode on the new plug will be more recessed in the cylinder. I assume no concerns there...would you all agree? Oh...and what a piece of cake despite being a transverse V6. Not sure if a J35 plug change would be any harder on something like an Accord or ILX with less space, but the last couple of times I did plugs on a transverse 6 was my Lexus with the 3MZ-FE and a Mazda with the Duratec V6...brutal in comparison. Dare I say I actually enjoyed this job.
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That’s a very pronounced chunk of metal on the ground electrode!

 

[Snagglefoot]

Here is an AC Delco 41-110 Iridium with 110,000 miles. You can see the very small disc of Iridium or whatever rare metal it is, on the ground electrode. That is about the same size as on the ground electrode of the NGK Iridium 1465 for this same application.

And here is the new design AC Delco 41-162 Iridium plug beside the old AC Delco 41-110 Iridium plug. The new design still has a small insert on the ground electrode but now has a small “collar” at the base of the center electrode.