Iridium may last longer, but I doubt you will get double performance. All you will get is smoother drive....

Yup, thread depth, plug size also......

Never change the heat range unless you have problems or you have mod the car kao kao. One step like 100bhp up....

---

Added on December 5, 2011, 3:53 pmDifferent brands have different design. All will say theirs is the best, so you have to read and find what you want....

This post has been edited by vr2turbo: Dec 5 2011, 03:53 PM

Try Denso then. Change accordingly using their conversation chart from your current model.

As far as I know ground electrode seldom wears, as for platinum and iridium center tips, they are so hard they will last.

Wah! you terror then, because in my turbo my iridium did not wear, only start to misfire after about 2 years of use.
Now on NGK platinum, after more then a year still running strong.
Last time when on normal plugs only the center electrode wears rounded.....never had any wear on ground electrode....

spare part shops don't carry them?

---

Added on December 6, 2011, 10:57 pmYup, daily ride for last 10 years. Second engine second turbine also....ha! ha!

This post has been edited by vr2turbo: Dec 6 2011, 10:57 PM

Oh! sorry, I was replying to you that mine is daily ride also, and on second engine as the timing snap on first engine, then recently after 9 years the turbine failed also...

They should have, anyway most of the ones here have.......

But rich......
or no wonder they are rich......

2 new plugs or 2 sets??

They should be able to tell you if they are Bosch dealer.
Anyway, for Bosch the heat range is reverse.
Jap plugs like NGK 5 - hot, 7 - cold, meand bigger number is cold
Bosch 6 - cold, 8 - hot, means bigger number is hot

Oh! you don't know about Hot plugs and cold plugs also. Well certain engine are designed to run hot, so they use cold plugs. The plugs helps to cool the engine. Or if running more on highway, cold plug is used.
Town driving usually hot plugs are used to help complete combustion.
Overall just follow your car manual recommendation on the plugs.
I posted the hot and cold just for your info because you want to use Bosch and if your car is running on NGK number 5 plugs and the Bosch dealer gives you a Number 8 Bosch plugs you may be confused. So now at least you should know NGK 5 is Bosch 8....hope you understand up to here?

Looks like you still don't get it. Does not mean cold is better. Cold plugs drive in town may build up a lot of carbon if the combustion is not complete.
The number are just for guide in changing from NGK to Bosch.
For Denso they use 18, 20, 22 and so on. Smaller number is hot, bigger is cold.

Nope, just follow your car recommended plugs....change Brands, then follow their chart...

Yup, now you got it ........ha! ha!

I think you got them backwards. Without misfiring the engine runs at it's optimum performance but not over.
If you compare with a misfiring plug then the performance is better.
Compared with a good running plug of another brand should be the same....