I was running The Red Line @ 25:1 in mine when i damaged the piston and sleeve, probably due to my own tuning error.
Fortunately parts were cheap and i got replacement parts.

I subsequently ran some Shell racing oil which worked ok. I remember it was very high viscocity stuff.

The Stihl ultra has only been available here in Australia for a couple of months. I have a bottle now and i'm itching to try it. My fuel can is currently holding 30:1 of Stihl HP mineral oil for break-in on both my OS and new Stihl whipper snipper. When that fuel is all used up i'll be using the Ultra.