Just recently I purchased a Stihl chainsaw. It was model#660 magnum. I just ruined it by using super tech 2 cycle oils. The piston was scored in a matter of weeks. I took it to a dealer and he told me that I had been running it without oil. I asked him if there was any other way. He assured me that I had not been using oil in it. My manual for the saw says a mixture of 50:1 ratio is needed. I assure you that that was what I used. This is not my first saw or my first piece of 2 stroke equipment. With all of that, a $400.00 piston, cylinder, and service charge was what a less expensive oil has cost me.. I assure you that from now on I will buy the Stihl manufactured oil...