I recently had a bad experience with a group of Stihl saws and one Homelite after switching to Royal Purple brand 2-cycle oil. I had used it previously on my McCulloch saw with no trouble and on my Echo weed whipper. When I tried using it on my big Homelite saw, the saw seized up. Since it was old, I thought it was just tired. A couple months later, I hired a sawmill to cut a white oak into timber. This tree was 40" in diameter. A friend cut it down and then I had to cut off the branches and split the main trunk which was too large for the sawmill. First, my Stihl 260 quit after 1/2 hour. I thought that maybe the plug fouled out. I then got out my 660 and started splitting the log. Since we were looking for 17' timbers, this was a long split through a big tree. I cut for about 10 minutes and the 660 stalled and would not restart. I went to my other 660 and resumed the cut. After only 5 minutes, that too quit. I took these saws back to the dealer to be looked at. In the mean time, I ended up buying an 880 in order to complete the job. They supplied the first tank of gas. I got through the rest of the tree with no problem. When I went to pick up my saws, the repair man a Weingartz told me that all three had scored the pistons and cylinders because of bad oil. I had been running 25 to 1 Royal Purple oil. This was the air cooled variety. The repairs amounted to just under $2000.00 for these three plus the Homelite that had burned up earlier. I contacted the dealer for Royal Purple. He said to bring in a sample of the fuel. Weingartz gave me a jar of the fuel from the tank of one of the 660s. The people at Royal Purple tested the oil and told me that it was actually more like 20 to 1 but thought that in the handling and transport, some gas may have evaporated. The rep said that the oil was indeed their synthetic oil and that it passed all of their tests. I wanted to know if they were willing to pay for all the damage to my saws. The rep at Royal Purple told me no, the oil met their specifications and so they would not pay for any damage. He did tell me that the oil was the right type for air cooled chain saws and that he had used it extensively in his weed whipper with no trouble. I asked if I had to sue to get satisfaction. He then said that once a law suit was discussed, end of discussion, I would need to talk to their attorney. Since getting the saws back, I have extensively used all of them with no trouble using the Stihl brand oil and cutting big oaks and ash trees. I no longer buy anything from Royal Purple, even though I was buying by the drum at work.