Does anyone know why they discontinued the well known and respected brand "Syntec"?
Back in the day, "Syntec" was their top of the line brand. With other manufacturers introducing new top of the line products (M1 EP, Pennzoil Ultra, etc.), Castrol went ahead and introduced Edge (already present in many other countries). I suppose having both Edge and Syntec in the lineup was causing some confusion among consumers. After all, Syntec "sounds like" something to do with synthetic, while Edge does not. Maybe some customers thought that Syntec was the better of the two products, while in reality Castrol wanted people to think that Edge is the better one.
So now it's all Edge, but one is Edge with Titanium and the other is Edge with SPT (Syntec Power Technology).
By the way, I'm not really sure that "Syntec" was such a respected brand. It is the brand that was associated with the whole NAD ruling against ExxonMobil (group III vs group IV/V) and was thought to be a "fake synthetic" by many.