Reasonable Iridium Plug change interval

[DrDanger]

What would be a reasonable Iridium Plug change interval?
I have Denso Iridium Power II's, which Denso rated for 30k miles back in 2014 or so when I put them in. I rechecked and now Denso Europe gives them just 20k miles.
I heard a lot of people claim 60-70k miles on them are no problem. Now the platinum electrode version is rated at 100k, so maybe they have them mixed up, but cant believe Denso either with their 20k.
What is your experience with Iridiums with/without platinum electrodes?

 

[E150GT]

I thought the whole point of iridium and Platinum was long life. If it's just 30k why not use copper ?

 

[Dave1027]

20k ? Copper plugs go longer than that.

Denso needs to sell more plugs. I'm sure that is line one on their business model.

 

[WobblyElvis]

My experience with the 6 or 7 cars I've had in the last 20 years was that all plugs last 100,000 miles or more. I have one car with iridium plugs and it functioned well for over 150,000 miles on the original plugs.

 

[StevieC]

DrDanger what does your manual call for and what are the factory plugs that were installed? Copper, Platinum or Iridium?
Let's start there and then we can determine Iridium plug change interval for your vehicle.

As for 20-30K miles for a single Iridium plug that can't be right, too low unless you have poor fuel quality in your part of Europe which could affect plug life.

 

[DrDanger]

Sorry I misquoted, per Denso:

https://www.denso.com/global/en/pro...e-parts-and-accessories/plug/basic/life/

Lifespan of iridium spark plugs
Not all iridium spark plugs are the long-life type, there are also some that have the same lifespan as a normal spark plug: 20,000 km (light automobiles: 10,000 km, motorcycles: 5,000 km).

Pretty interesting read to say the least...

StevieC,
my cars manual was translated poorly and has multiple misquoted figures in it, 30k km OCI's, going to the dealer for a windscreen wiper changes and so on.
I would not trust it as far as I can throw it. I will stay with Iridiums as they perform better than previous copper NGK's.
My car is a 2004 Peugeot 407, EW10J4 engine, DOHC 16v, 2.0l converted to LPG.

 

[SirTanon]

I had a set of Iridium plugs last 215,000 miles in my Fusion.. take that as you will..


100,000 miles is generally considered standard, and only 30,000 miles is a cake-walk for iridium.. you'd be wasting your money if you replaced them that often.

 

[Oro_O]

The Denso Power models have a thinner Iridium center electrode and a nickel ground electrode and are designed for performance applications. They can last longer than that, but tuning often reduces it. Denso is pretty transparent about this.

If your car is unmodified and your goal is less maintenance, what you probably want to buy is the Denso Long Life model. To see if your Denso Power models need changing or can go longer, pull them out and inspect them. It's application-specific and no one can honestly tell you without looking at your plugs.

Real-life experience is going to mirror the advice on the table already - thin-wire, nickel ground performance iridium modles wearing out in 30k miles, and thicker long-life, platinum-ground models lasting upwards of 200k in undemanding applications.

 

[StevieC]

Originally Posted by DrDanger
Sorry I misquoted, per Denso:

https://www.denso.com/global/en/pro...e-parts-and-accessories/plug/basic/life/

Lifespan of iridium spark plugs
Not all iridium spark plugs are the long-life type, there are also some that have the same lifespan as a normal spark plug: 20,000 km (light automobiles: 10,000 km, motorcycles: 5,000 km).

Pretty interesting read to say the least...

StevieC,
my cars manual was translated poorly and has multiple misquoted figures in it, 30k km OCI's, going to the dealer for a windscreen wiper changes and so on.
I would not trust it as far as I can throw it. I will stay with Iridiums as they perform better than previous copper NGK's.
My car is a 2004 Peugeot 407, EW10J4 engine, DOHC 16v, 2.0l converted to LPG.


I wish we had a comparable model here that we could look up for you. As a comparison my van uses Iridium and last 160,000km but it has a coil on each cylinder. Not sure if that is the same as your engine (coil on each cylinder). They aren't double tipped Iridium either. Just a center electrode has iridium on it the ground electrode is standard metal.

I could message my uncle in France and see if he can find out when he's at an automotive parts store next. He's pretty hands on with his vehicles.

 

[DrDanger]

Thanks all for the quality replies.
I will check my plugs and go from there.
My copper plugs were borderline good at 15k miles, so I guess Denso is trying to
increase sales a bit

 

[Snagglefoot]

Originally Posted by WobblyElvis
My experience with the 6 or 7 cars I've had in the last 20 years was that all plugs last 100,000 miles or more. I have one car with iridium plugs and it functioned well for over 150,000 miles on the original plugs.


Ditto. 100,000 miles should be no problem. I had 180,000 miles on my AC Delco's.

 

[Snagglefoot]

A good Long life Iridium plug has a small platinum disc fused to the ground electrode and a center electrode consisting of a fine Iridium wire.

 

[Snagglefoot]

Thanks all for the quality replies.
I will check my plugs and go from there.
My copper plugs were borderline good at 15k miles, so I guess Denso is trying to
increase sales a bit

[/quote

If you want a safe bet may I suggest you cross reference your plugs to NGK Iridiums. You can use the Rock Auto website to confirm the choice based on your year and model of car.

www.rockauto.com

 

[Pelican]

Originally Posted by DrDanger
Thanks all for the quality replies.
I will check my plugs and go from there.
My copper plugs were borderline good at 15k miles, so I guess Denso is trying to
increase sales a bit

I had a Subaru OutBack 2001 and the spark plugs were to last 160,000Km, I'm very surprised that yours only last for 20-30,000Km this is 1960 technology!

 

[DrDanger]

Originally Posted by Pelican
Originally Posted by DrDanger
Thanks all for the quality replies.
I will check my plugs and go from there.
My copper plugs were borderline good at 15k miles, so I guess Denso is trying to
increase sales a bit

I had a Subaru OutBack 2001 and the spark plugs were to last 160,000Km, I'm very surprised that yours only last for 20-30,000Km this is 1960 technology!


The garage said I could go a bit more, but wanted to put in Iridium anyway, soo

 

[StevieC]

If there is one cylinder easier to get at you could always pull that plug and monitor in 20,000km intervals until you find the right change interval for you.

 

[DrDanger]

Originally Posted by StevieC
If there is one cylinder easier to get at you could always pull that plug and monitor in 20,000km intervals until you find the right change interval for you.

Thanks Stevie, will do.

 

[BobGoblin]

My NGK Iridium sparkplugs are due for change every 150.000 km, by the user manual.

 

[Snagglefoot]

You could always go ahead and change the plugs and get it over with. Use NGK Iridiums and repeat in 100,000 miles. Done.

 

[MolaKule]

Owing to the fact that LPG has an adiabatic flame temperature 3575F and gasoline has a flame temperature of 3880F, one would think that Iridium plugs would last longer in an LP fueled vehicle.