Iridium heat range answer from NGK

[Stig / Major Tom]

Recently I asked NGK if we need to use a cooler iridium plug when switching over from a standard spark plug.
They said, no - the heat range of a "7" standard plug is the same as the heat range of a "7" Iridium plug.
(ie: they've already taken into account the heat properties of both plugs - and while an iridium plug is 'hotter' than a standard plug - they've built both  "7" plugs to be the same heat range - otherwise their cross reference charts would be ruining engines across the globe)

 

The heat range remains the same between the standard plug and Iridium plug so if you use a CR7HSA the iridium part number would be CR7HIX.

Rob MacDonald
Technical & Training Specialist
NGK Spark Plugs U.S.A. INC.

FYI- these are the proper NGK's for the LIKE 200i (CR7HSA, iridium/CR7HIX)
       (DENSO:  U22FSR-U, Iridium/IUF22)
 

[Grumpy old man]

I ran an Iridium 9 plug in my People 250S for a year or so and when my mechanic looked it over suggested a cooler heat range lots of white powder evident so I moved to an 8 and other than an occasional burp starting it has been good.  of course it's only been run 5,000 miles so as far as life/ wear can't answer.   Jim.

[Stig / Major Tom]

I ran an Iridium 9 plug in my People 250S for a year or so and when my mechanic looked it over suggested a cooler heat range lots of white powder evident so I moved to an 8 and other than an occasional burp starting it has been good.  of course it's only been run 5,000 miles so as far as life/ wear can't answer.   Jim.

Thanks for the feedback....I will keep an eye on the plug condition.
Stig