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
5" exhaust, zoodad, blue spring, Airaid intake, 6.4 starter, 2.5 f/coils, adj Trac bar, 2" r/add-a-leafs, egr delete, snow plow fan clutch, csf 6028 intercoolerr, DC 185 alt, Bilstein 5100, Barder '03 turbo rebuild w/RR billet wheel, SCT SF3 tuner, F-Detroit Truetrac, R-Detroit Locker, 4:10 gears, hawk LTS, LT315/70r17 Duratracs, Amsoil Gear lube, Delo 400 LE 5w30 diesel, Delo ELC, archoil, bpd ficm, BPD oil cooler, dynatrac pro steer ball joints, arp studs, oem gaskets, HD water pump, stc, plugs, stand pipes, 6.4 banjo bolts,
Last edited by Baddestt; 11-18-2008 at 10:12 AM.