I'm sure Amsoil is good. I have used it in my 900 hp Turbo 4.6 Mustang with excellent results.
As for diesels, I'm not convinced that Amsoil is the "best" out there, and can you REALLY justify paying all that money for Amsoil diesel synthetic when there is evidence that Mobil 1 delvac/ Turbo Diesel Truck 5w40 is just as good or better for a cheaper price and more readily available. And there is just no comparison as the way the truck runs when comaparing Mobil 1 TBD 5w40 and Shell Rotell 5w40. With the Mobil the 6.0 just runs smoother and quicker starts. The Mobil is a true PAO synthetic as opposed to the Shell Group 3 highly refined petroleum.
IMO, I just feel the Mobil 1 is one of the best alternatives to Amsoil and Shell Rotella T 5w40. There have been issues with Shell Rotell T 5w40 giving not so good oil analysis after just 5000 miles during towing or HOT summer temp operations.
In any event, we will all use what WE think is best for our individual 6.0. My brother swears by Royal Purple and he uses it religiously in his '06 Duramax...we argue back and forth all the time
'07 F-250 PSD 4x4
. S&B, 5" exhaust, zoodad, blue spring, '03 Turbo, 6.4 starter, 2.5 f/coils, adj Trac bar, 2" r/add-a-leafs, egr delete, DC 185 alt, Procomp shocks, SCT SF3 tuner, F-Detroit Truetrac, R-Detroit Locker, 4:10 gears, LT315/70r17 Duratracs, Amsoil Gear lube, Amsoil FE ATF, Delo 400 LE 5w30 diesel, Delo ELC, archoil 9100/ar6200, bpd ficm, arp studs, oem gaskets, HD water pump, stc, plugs, stand pipes, 6.4 banjo bolts, monitor, new oil cooler, coolant filter
Last edited by Baddestt; 11-18-2008 at 10:12 AM.