Originally Posted by gsxr

All true. Rotella Syn is better than most dino oils however it is NOT, IMO, suitable for extended drains. I would change the Rotella Syn by 5kmi at most. If you want to do extended drain intervals (which I do), you really need a proper Group IV or V synthetic, which would be Mobil-1, Amsoil, Red Line, and a few other top-shelf synthetics. Mobil is the easiest to locate and similarly priced to Amsoil's dealer pricing, Red Line is nice stuff but pricey. I use Delvac-1 in my vehicles (both diesel AND gas.)