mtnboydl

It looks like the OEM plugs are the NGK 5547 plugs which are platinum.

Is there any advantage to upgrading to iridium plugs? What have you guys used?

Maybe the plug geometry is such that you only want to use the 5547 so that the coil pack can connect properly.

MP4.2+6.0

I don't try to outthink factory on plugs. If motor is turbo or supercharged (...not in your avatar or sig...) I would definitely not be going non OE spec., which Audi has revved a few times already IIRC on the 4.0T.

Iridiums are basically harder and longer lasting. But, they also don't conduct as well as platinum. Platinum in turn does not conduct as well as copper, but copper can't run near as long as platinum. First time I ran into Iridium plugs was my 2004 Toyota Sienna V6 with 100K change intervals. Plugs in back of V were also a nightmare to change in back part of motor sideways against firewall high up. I can see why they went Iridium there. On Audi's I prefer to see them every three or four years anyway just to get a sense of fuel burn, oil burn, etc. Used plugs can tell you a lot about engine health if you know miles on them and how to assess visually.

mtnboydl

Not sure why the sig doesn't show up. I've got the 4.2

mtnboydl

Maybe the sig only shows when posted from the desktop version?