I have been a frequent lurker and occasional poster here at BITOG for about five years now. My name is Steve Lang, and a few of you have known about my work as a car dealer and former auto auction owner here in northwest Georgia. I am also co-developing a long-term reliability study that has been well publicized at Yahoo and other online publications. http://tradeinqualityindex.com/ Long story short, I am developing an article tentatively titled, "Should You Change Your Motor Oil Every 15,000 Miles?" I realize there is no easy universal answer to this question and, with that said, I'm more interested in providing an article that covers as many bases as possible. Even if that requires an answer of, "It depends...", it's better to give folks a specific answer instead of blank generalizations. If any of you know or have specific relationships with industry professionals who could answer this question as it pertains to specific types of engines, it would be a great help. Like a lot of you, I have my own assumptions and personal experiences. But I think it's always worth our time to get advice from experts who have the scientific background to help give the right definitive answers to our questions. That's one of the innumerable reasons why I have been a part of this community for over five years now. Thanks for everything. If you Google "Steven Lang and cars and Facebook" online, you will find an easy way to contact me. I'll also respond here as well. All the best!