Iridium is still a far superior plug. Much longer life, stronger spark output (conductivity), etc. In some cars though they are not necessary, like some low boosting 8's. So if you don't want to fork over the $60.00+ price tag for 4 Iridiums then you can pay $10.00 for a pack of coppers and have them essentially do the same thing (but they need to be replaced sooner).

So, the iridium is still a better plug if you can justify the price tag.

 

And are cheaper in the long run.

 

So a good estimate for change interval for daily driven, moderate boosting ride would be:
Iridium =<8mths?
Copper=<5mths?

 

I would want to change the coppers out at least every other oil change, the iridiums I have seen people run for years and still be alright. Just pull them every once and a while, check the gap and possible clean the carbon off of them and your set.

 

OEM Iridiums are good for at least 30k miles. If you have mods, you'd wan tto consider going to 1 step colder coppers, but like everyone pointed out, you;ll need to change them often. BTW, Iridiums cannot be gapped!

 

Cool.

 

If they cannot be gapped then why does everyone I know including myself gap their iridium plugs. They usually come pregapped at .032 which is more than anyone I know runs on an Evo. If you carefully gap them by using a spark plug tool, not the circle one, don't touch the iridium electrode and check your gap with feeler gauges carefully you will be fine.

Taken from NGK's website!
http://www.ngksparkplugs.com/tech_su...p.asp?mode=nml

FAQs - Spark Plugs

Q: Do I need to set the "gap" when installing a new set of plugs?

A: Maybe. A spark plug part number might fit hundreds of different engines from many different manufacturers. Although the NGK factory will set the gap to a pre-selected setting, this may not be the right gap for your particular engine. The incorrect plug gap for your engine can contribute to a high rate of misfires, loss of power, plug fouling, poor fuel economy, and accelerated plug wear. It is always best to check the gap against the manufacturer's specifications. If adjusting the gap on fine wire or precious metal plugs such as platinum or iridium be very careful not to apply any pressure or prying force to the fine wire center electrode or insulator as they can be damaged. The gap should be adjusted by only moving the ground electrode

 

I always gap my iridium plugs. Do a litle bit of research on snap-on tools website and youll find some spark plug gapper tools. I think I paid $5 for it. It lets you adjust the gap without touching the electrode.

 

What spark plugs would you recommend on a 2.3 stroker engine? Evo 8 and which gaping i run 21-22 on stock turbo.

 

Iridium is the way to go. I pulled the stock NGK iridium plugs out of my IX at 43k miles and they were still perfect. A lot cheaper in the long run than constantly changing out copper plugs.

 

if i were you id go with iridum... especially since you havent changed them in 20000 miles... unless you want to be constantly changing them with copper ones. just the way i look at the situation.

 

As far as damaging the electrode on iridium plugs- I would think you would have to apply a lot of pressure to do any damage right? Is the whole tip made of iridium or is it coated?