Man, I think that is a great question. I go with the syn due to the reasons already mentioned but I do wonder how torn down engines compare if you did oil changes within the recommended periods. I'm would think an unbiased study or studies on this have probably been done. I have seen supposedly unbaised data about the temp improvements on motorcycles using syn vs dino but nothing on tear down comparisons. I used syn3 unitl reading posts at HDTimeline. Smitty, Glider, and others convinced me to use other lubricants in my bike.