Not sure if you guys noticed. I just pulled out my Denso Iridium plugs and noticed heavy wear on plug 2 & 4 (the plugs where the coils are over it, 1& 3 have just plug cables).

I'm surprised to see a nice cave-in in both plug 2 and 4.

Any one experience similar wear?

NOTE: These plugs had covered 20k km

 

Sure you didnt squeeze too hard with the pliers when you were gapping them?

That is weird. I just checked mine the other day and they did not have an indentation, if anything I remember a slight bump where the electrode spark would contact the metal surface. Not sure though...

 

Nope, I didn't even gap them .... but since it's consistent on both plug 2 and 4, I can only speculate that those plugs under the ignition coil are receiving a much strong spark that 1&3 which are on plug cables.

 

I've never experienced wear like that, but I have seen the ground strap be come rounded and eroded in a short amount of miles. I associated this with running Leaded Race Fuel with a high concentration of MTBE (trick 114L)

 

Will running lean cause that ? But then again, it's only on 2 & 4 !