Stihl Ultra is an FB rated 2 cycle oil. The JASO (Japan) scale of 2 cycle oils is FA FB FC & FD. FA is obsolete, so we have FB FC & FD ratings. Generally, the higher the rating the better the oil, because the oil will have more additives. So, when tested the FD oil will outperform the FB oil. This is measured by wear on metal and temperature (I'm summarizing).
I'm guessing it is more cost effective to have less additives (Stihl Ultra). Echo oil looks good, it is mostly FD (143-147). Husky too (203-204). I don't think Stihl is on this list but Stihl Ultra is rated as an FB oil by the industry. Maybe better to run Husky or Echo oil in your Stihl chainsaw? Here is the list. Poulan Pro is an FD oil, too. Note: they are listed in alphebetical order by the supplier name - the 2nd row.
https://jalos.or.jp/onfile/pdf/2T_EV_LIST.pdf
I'm guessing it is more cost effective to have less additives (Stihl Ultra). Echo oil looks good, it is mostly FD (143-147). Husky too (203-204). I don't think Stihl is on this list but Stihl Ultra is rated as an FB oil by the industry. Maybe better to run Husky or Echo oil in your Stihl chainsaw? Here is the list. Poulan Pro is an FD oil, too. Note: they are listed in alphebetical order by the supplier name - the 2nd row.
https://jalos.or.jp/onfile/pdf/2T_EV_LIST.pdf