Ok one more time. Has it been proven or disproven that certain types of oil (synthetic) more can cause bearings to slide or skid because. Roller bearings or ball bearings included. This is an old Harley shop argument and some Japanese builders say this is an issue as well. Many have run dino or synthetic on all types of bikes and automobiles with no issue but is there any real evidence it is a concern. My recent post in the bike oil forum shows that even Harley Davidson says this is still an issue with some brands of synthetic oil.