I just checked one of the plugs in a new to me F150 with a 4.6 and it had NGK Iridium plugs, the truck has 122K on it. It runs fine and smooth and they look like they have been in their awhile. Does anyone know anything about them?
Denny

 

Well the plugs were changed sometime in those 122k miles. NGK makes good plugs, I run them in all my Yamaha outboards and some in small equipment. I had a set of Iridiums in my 25hp the last few seasons. Could not tell any difference in idle of running performance with the Iridiums so I am back to plain old copper NGKs. But the rub is the engines I use them in specifically specify NGK plugs. I have found some plugs just work better than others and the OEMs tend to know what brand plugs that work well in their product. Fords seem to like their Motorcraft and Autolite plugs.

Last set of plugs I put in my dads V10 before he traded it was Autolite Iridiums. He ran them for 3 years or so and there was no noticeable change at all vs the paltinums. I have a set of Autolite Copper plugs ready to go in my V10. Copper plugs have th eleast resistance so I'm interested to see if there is any difference with them.

 

I have never seen them before and after doing some Googling they look like good plugs and the one I removed looked in good shape so I think I won't worry about them, the boot was also in good shape and was probably replaced with the plugs. After reading about them I'm glade I didn't try and check or adjust the gap, looks like it's easy to damage them.

Denny

 

They are tougher than they look. I've haven't broken one yet.