Oregon SELL oil but they do not MAKE oil
AFAIK Oregon only make metal parts like chains, Bars & blades.
Everything else is made for them.
There are two basic grades of premix 2 stroke oil
Land & Marine
and 3 types
Mineral, Semi -Synthetic & Fully Synthetic
Castrol only MAKE oil & Grease so if their oil says it is suitable for your engine, it is suitable for your engine.
Down here we have only one oil refinery Castrol.
We have 50 different blenders who blend different products from CASTROL base stock
Every mower company sells their own brand oil.
The only difference in most of them is the colour die Western Oil puts in there.