Well guys, as an experiment (along with some laziness) I just put 10K miles on the oil (Mobil 1 5W40) in my 617 turbo (I normally go a maximum of 5-7K highway miles). These 10K were all highway miles, accumulated over about two months. When I finally changed it a couple of weeks ago, I sent the oil off for analysis. I'm still waiting for the results. At the risk of introducing some actual facts into this discussion, I will post the results when I get them.

We'll see what the analysis results say, but I don't expect to significantly extend my oil change interval (beyond about 7K). I still don't think I would be comfortable with 10K oil changes in a diesel, and I certainly wouldn't go much over 5K if I was doing any significant city driving. I just consider it cheap insurance. Hopefully, I will have the analysis results soon.