Not all Stihl oil is garbage . Ultra is garbage although it's niche was 4mix engine usage . Even there it leaves as lot to be desired . Ultra HP is a overpriced premium synthetic with average performance . Stihl Premium a old production line of Group III oil is above average performance oil . Have used it for years in a MS-260 , ms-360 & ms-660 models , back in The day no problems . There are numerous better oils available Motul , Amsoil , Red Armor , Echo & even Shell-T . I now run either Amsoil or Shell in all 2 stroke applications .The most important fact is to tune your saw to the mix ratio you choose for your saws use application . The operating characteristics of a felling & bucking saw , varies from that of limbing or milling saw . I pretty well run all homeowner 2T hand held units @ 50:1 . My pro grade or commercial saws run 44:1 & my milling & hot saw runs 32:1 all with good quality non ethanol fuel .