I have Castrol 5w20 in the sump of my F150 right now. I have not seen a "blend"...I assume you mean synthetic blend...on a Castrol 5w20 label.
As for the Castrol 5w20 I'm running, there are some pretty good analyses on the Used Oil Analysis board.
I've been thinking about trying this oil myself. Maybe I'll give it a try after I see how the Mobil 1 0w-20 does. Here's how I look at it:
1)It's cheaper than full synthetic.
2)It's 5w-20, which almost all UOA's have shown great results for.
3)It's part Castrol GTX, which is one of the better dino's.
4)It's part Castrol Syntec, which is one of the better synthetics as of late(at least the GC).
Heck, sounds like it should be a pretty good oil!
I'm waiting to see an inspection data sheet on this oil to see if it's worth the extra money over the GTX. GTX already meets the 153-H Ford spec, so unless the Syntec blend offers better cold start or heat shear protection, I'm sticking with GTX that I can catch on sale for $1.38/qt.