This engine was run on a Grp III from 2005 till it stopped but that was 9 years ago, oils have improved a lot since then.
Mobil 1 0w20, 0w30, 0w40, 5w30 ESP, PU 5w20, PU 5w30 all have done a great job at keeping them clean. One has gone over another 100K since cleaning and it didn't make it much past 80K originally and its staying clean.
I cant say what other brands will do or wont do i haven't tried them but i understand DNewtons point. Under normal circumstances these are a very long life oils and draining them out a 5K would be a real waste but IMHO not on these particular engines and a couple of others.
Just from my own observations that front head runs hot, very hot! Honda changed it in 08 to add another cyl in the mix on the other bank and shut one off so they knew something was afoul IMO.
The other thing is, when the front cylinder begins to cook the tiny PCV gets clogged as does the valve covers internal passages and this just makes things worse.
The non VCM Honda 3.5 is a very good engine, smooth and powerful for a V6 with a nice power curve but these are a nightmare, IMO they ruined this great little engine then charged a premium for it, all for a of a couple of MPG.
What little was saved on fuel was eaten by shorter OCI, a ruined engine or a massive and expensive cleaning job. Thats called negative return on investment!
Valve cover front cylinder.
Location of PCV.
Tiny internally vented PCV valve.