Good info fella's! I have run the orange bottle for almost all my saw year's. Thought it was alway's good enough. You guy's more so recntly have aroused my curiousity about other oil. Still didn't switch had never thought I had problem's. But over my year's on this site I have learned alot about more thing's. I have alway's done my own mechainc work on everything I own, except saw carb's, and fuel line's etc. I learned how to do more on this site, and my 660 need's a carb kit. Im gonna try, and do it. I am hell on wheel's at servicing them, and filing. Today troubleshooting the 660. I pulled the muffler knowing all was good in there, but hadn't peeke'd in awhile. Everything I own all saw's, and breed's I am seeing carbon build up starting. That tell's me tried, and true orange bottle isn't good enough anymore. I am sold bought some hp ultra. Don't know why it took so long. Grew up on two stroke dirt bike's, and alway's ran, and found synthetci was the key!:msp_thumbsup: