Do iridium spark plugs not last long?

[repairman54]

Years of driving Co. fleet Express vans, 4.3 motors, OEM plugs would start misfiring on cold morning start ups at around 160k miles. Misfire would go away after fully warmed up. Typical fleet maintenance would only change plugs with a constant CEL on.
I've had no issues with OEM iridium plugs going 100k miles in GM and Fords in stock tune over the years in my personal vehicles.
Put 5k miles on them in a carbed 2 stroke 700cc snowmobile, and sold it with those plugs in it. And 2 stroke carbed sled motors are tough on plugs.

 

[ARB1977]

Toyotas 3.4LTT runs iridium’s. Requiring 40K intervals to keep emissions happy.

 

[zzyzzx]

Just because a plug can theoretically last 100K miles, or more, doesn't necessarily mean that it doesn't need to be removed and regapped periodically. At least my experience with double platinums suggest this.

 

[2strokeNorthstar]

My Nissan's spec NGK laser Iridium for 105K. Why 105 - no idea. I have run them 100K several times and they always came out looking OK. Posted the here last time I did it - general consensus was they looked good.

My Nissan specs them for 110k. Another random number thay I don't know how they came up with

 

[Astro14]

Toyota specifies a 100,000 service life for iridium spark plugs. I’m changing them early, at 80,000 - to preclude any problems with seizure due to age.

80,000 mile iridium spark plug above. New below. Looks like those plugs could have been run for a while longer. A LOT longer.

Spec: 1.1 mm
New plugs: 1.1 mm
80,000 mile plugs: 1.1 mm

So, yeah, genuine Iridium plugs DO last a very long time.

 

[2strokeNorthstar]

Toyota specifies a 100,000 service life for iridium spark plugs. I’m changing them early, at 80,000 - to preclude any problems with seizure due to age.

80,000 mile iridium spark plug above. New below. Looks like those plugs could have been run for a while longer. A LOT longer.

Spec: 1.1 mm
New plugs: 1.1 mm
80,000 mile plugs: 1.1 mm

View attachment 243195


So, yeah, genuine Iridium plugs DO last a very long time.

I found the same in our Nissan when changed the first time around 90k. Almost no measure able wear. NGK plugs from the factory are a quality item. I put new ngk plugs from the dealer back in. About 90k on this set now. Not sure if I'm going to change them since we plan on getting rid of the car in the next year.

 

[loneryder]

Yeah. I saw an article where Mercedes and maybe a couple others would fire the spark plug 5 times to eek out the best flame kernel and the most even combustion

True. They recommend 50k change out but most people say they look fine at swap out. They fire multiple times each cycle as do the direct injectors. Maybe that's why their engines don't suffer from fuel dilution?