They are definitely on the lower end of the 30 grade scale. Both apparently perform very well on the Seq IVA test. Other then that, not sure. Product data sheets only tell you so much, and Castrol doesn't provide that much info.
Hey, some engines like that viscosity, but I never knew it was that thin. See, I run GC in 2 vehicles that we have, an Eclipse GS with 155k miles, and an LS1 Trans Am with 175k+ miles. That's why I chose GC for them.
So, I kinda like something in the 11+cst range. I should have clarified
I finally saw this stuff for sale this weekend. $34 for 5 qts., ouch! Who wants to start a betting pool on when they are going to cut the price to get people to buy it???