It's a little slow lately so I thought I would put out a couple of lingering questions I had. I had been using the Opti-2 2 cycle premix in all my 2 cycle equipment and I have been really happy with it. The guys at the local Stihl dealership told me they see a lot of sludge in the crank cases of saws running this. Whether or not this causes the case to be split anyway is a different question altogether. I bought a bunch of Stihl HP Ultra since it is the only fully synthetic mix I know of. I see Stihl will double your warranty (non-commercial) if you use it. I don't care for the way it smells but oh well. When I bought my 346xp a few months ago they fueled it with the Husqvarna semi synthetic. All 3 seem fine to me. I am not a brand loyal person most of the time. I do run a lot of synthetics though. Anybody have any input into what they are running and why?