Regarding your comments about "cleaning up' and "leaving crap place you don't want it". Some of that may have come from some true stories about gents who where converting over to synthetic oil and were to use a crankcase cleaner designed to "clean" things up. I do recall the brand, but won't mention it here becuase they have since got it figured out. Needless to say, the cleaning did such a good job it gummed up the works.
I my case, when my 1980 450 SEL was 45k young 10 years ago I went to synthetic and have had no problems. In fact, everytime the valve covers are off for PM, it's as clean as a whistle under there.
I converted my G-wagen to synthetic last year and no problems there either.
Probably the single important thing, regardless of syn vs non-syn oil, is a regular PM that includes oil and filter (high quality)changes. Beyond that the debates begin. Actually, I think the oil companies like it because it gets us all talking about oil changes and that means buying their product. Gotta love capitalism.
As an aside, we could all take a lesson from the aviation industry. Came across an article that describes the process of pulling oil filters apart and inspecting for metal. Race mechanics do this all of the time. Interesting idea. I do know that most fleet deisels are on oil analysis programs, but I wonder if it includes filters?
Good luck. J.R.