remember that old thread where one oil company was complaining that another oil company was using regular dino oil and calling it synthetic? The result of that lawsuit turns out that they have something called type 3 base oil, which is made from dino oil, but is allowed to be called synthetic.
Well from what I understand, that is what Rotella synthetic is made of.
Other oils like Mobel delvec 1, Amsoil, Redline, etc are made from Type 4 base, which is real synthetic base.
I am not the expert here on Oil, I am just am Amsoil prefered customer for personal use.