Ironic how the Stihl patent solves a problem and allows very low oil mix ratios for the 4-mix yet they cling to the 50 to 1 so they have I mix ratio across the product line.
These were the issues that were expressed by many when Stihl first began to announce the 4-mix and they remain.
"Ironic" and "Cling"? I think it's called "practicality". Heck, we have enough problems telling customers to make sure their mix is 50:1 (not just add more to the 30% full container!), never mind maintaining two different containers and mix ratios.
Stihl tells us that Ultra is o.k, to 80:1 in blowers, but they are reluctant to publish this because it will result is the inadvertent use of 80:1 in the other equipment. And they have tested thier saws at 80:1, and aren't ready to go there.
We're not seeing any issues in any 4-mix engines using Ultra or other true synthetic mixes at 50:1. I use it in mine personal equipment and everything is looking peachy. Even the Stihl semi-synthetic seem to be working out o.k. but it's definitely "sootier" inside.
Blowers had some initial problems with the blower exhaust valves, but they were updated to stellite a year or two back.