Originally Posted by JamesM3M5
Possible but doubtful. Car only has 36,500 miles, but is a 2008 build. No leaks, nothing else funny about it, all stock. It's out of warranty now, so thankfully he didn't take it to the stealer.
I think the sooty buildup is poor fuel combustion, not oil. The piston crowns look pretty clean on large portions, and they look relatively the same across the 4 out of 6 I looked at. The plug is sooty around the area that is directly adjacent to the injector. I'll shoot some photos.
If this doesn't work tomorrow, we will have to pull the intake and/or do some leakdown testing.
My valve cover gasket leaked in cylinder 6 at 32k miles so anything is possible. Hopefully that's not the issue cause it's extremely time consuming to do that job.