Hi all,

2007 STi.
I have a new set of spark plugs now arrived, just a quick one...

What would be the best lube to put a smear onto the spark plug threads? Copper grease?

 

I think spark plug manufacturers specifically say no to copper grease.

 

no lube, just reverse wind/feel until they seat before tightening so that you've no chance of cross threading them

 

May be abort mission anyway....I've purchased NGK ILFR7H Laser Iridium plugs, but my engine builder told me today he's seen problems with these on Subaru's and that he uses NGK Laser Platinum plugs.
It's a fully forged 2.5 with standard heads. 342bhp and 410lb ft.....

Not sure if I want to fit them now??!!

 

It's all I've ever ran in mine without issue...over a hawk sti and now a hatch sti across 7yrs

 

Platinum plugs far better

 

It says on the box that the central electrode is Iridium, and the ground electrode is Platinum....does that make any difference?

Says copper below but I took it from google images.

 

the std Factory plug is an ILFR6 the ILFR7 is simply a cooler running plug designed to cope with higher boost / cylinder temps and we have supplied & used them for circa 15years in all kinds of projects from std road cars through to highly modified variants..........NEVER had an issue........

be intrigued to know the exact plug your engine builder recommends, based on what issues and who it is

 

also used NGK plugs for many many years without any issues

 

He didn't say what issues he'd experienced, only that he's always preferred Platinum personally. I called him to ask advice on if I should lube the threads whilst fitting. He didn't say not to fit Iridium,,,,and added that 7 is a good range for a forged / mapped build.

I suggested "nipping" the plugs down....he said "a very gooood nip!"

 

I think you or him is getting confused with the 2.0 plugs that are a PFR code but totally wrong fitment for the EJ257 application and can actually cause issues in the wrong installation??

 

Plugs fitted today, wow cylinder 4 was awkward, but soon learnt that having the handle of the socket towards the bulkhead was a win for me. A combo of a wobble and various extensions for that one. Getting the coil pack back in was also tricky, so close to the chassis rail.

The old plugs were indeed NGK Iridium ILFR6B and had done approx 50k miles. They all looked identical and a very healthy colour which was nice to see.

I see a 7 plug runs colder, but what does that mean as such? Gains of any kind?
Have to say, I took the car out and it loves the new plugs

 

as above its cooler running so resists pre-ignition / detonation better and copes with higher boost / power targets..........