I use Klotz R-50 because Andyshine77 told me to several years ago.
I use it at at 36:1 because I'm too cheap to use it at 32:1.
(Actually it seems to run a bit cleaner and less pungent)
I have found something interesting concerning the Klotz R-50.
I haven't funked a carb or had any fuel line troubles since I started using it.
The Poulan Lovers GTG was last weekend and it had been over a year since I ran some of the saws I took to it.
They sat with fuel in the tank, (87 octane ethanol at "up to 10%") since the last PLGTG and every one of them started in just a few pulls and ran like I cut with them the day before.
I don't know if the Klotz has a stabilizer in it, or if the esther synthetics are their own stabilizer but I used to have quite a bit of funked carbs and snarked fuel lines when I ran other oils.
I even had a string trimmer deteriorate the primer bulb and totally funk the carb in just over a month with a good quality oil just before I switched to the Klotz.
Mike