Well, after some hemming, hawing and procrastination, I changed the
plugs on my 2018 G90 3.3TT on Sunday.
The car had 42,732 miles on it, and judging by the appearance the old
plugs, it was definitely time for them to be changed. All 6 of them had some degree of discoloration on the
ceramic core, eminating from where it joined the metal base. Although the car ran fine prior to changing the
plugs, it looked like the spark was escaping at that joint and scorching the
ceramic.
I bought the car with 23k miles on it, so I don't know if the previous owner had a very heavy foot or what, but the
plugs were toast.
The process itself was very fiddly and a pain in butt, but I got 'er done. It took about 3 hours with me and a buddy working on it, but we ran into a variety of minor snags that took up time. Nothing I do ever goes as smoothly as it does on the YouTube videos.
The biggest PITA was getting a deep 5/8" socket out of the passenger side middle
spark plug bore (the one under the intake plenum). The jointed
spark plug socket I bought on Amazon for $10 was too floppy to effectively torque the plug, so I pulled it out and used a deep non-jointed socket and a swivel and extension to snug the plug. The problem came when I tried tried to pull the socket out of the bore and it pulled off of the extension.
When they say space for your hand is tight for that plug, they weren't kidding. 30 some minutes, and an impressive variety of Anglo-Saxon 4 letter words later, we got it out of there.
I bought 6 NGK 97976 SILZFR7A9G Laser Iridium
plugs directly from NGK for $80 plus tax and shipping for a total of $90. I also purchased a set of swivels and wobble extensions from Harbor Freight, so I spent a total of about $110 to do the job.
Considering my local dealer wanted $635, I'm pretty pleased with myself.
As an added bonus, the car is much quieter at idle. It had a fairly loud valve rattle before I changed the
plugs that has been reduced significantly.
All in all, my advice to you if you have a 3.3TT engine with the original
plugs in it and more than 42,000 miles on the clock, suck it up and change the
plugs.