I,m glad were finally getting this oil thing figured out. Your right,, Echo,s Power Blend and Red Armor are Semi Synthetic, the Red Armor says it will keep gas good for up to 2 years ( that,s strechin it I,d say) Both carry the FD rating, which is the highest you can get. The Stihl Ultra is the Full synthetic. The reg. orange bottle stuff is regular mineral base with a gas stab. Both Stihl,s oils are a FB rating. I have some Stihl equipment and have used all of the mentioned oils, I have had good luck with all of them. Over the years I,ve probably used more Echo Power Blend and Lucas the most of all. I guess to sum it all up, some people like mustard and some like ketchup. Either one will work.