I sell AMSOIL and ran it in my Harleys and my old DMAX, so I always thought it was no question! However, after seeing some posts on this site about AMSOIL not running so good in the 6.4 PSD, I decided to conduct a little further research. I ended up spending $88 by going with the Mobil 1 Synthetic 15W40 for "Turbo Diesel Trucks". Then I spent some valuable time talking to one of the Ford Diesel Techs at one of the local dealerships. He suggested to always run the Motorcraft Oil Filters, but synthetics just aren't worth it in the new 6.4 because the oil needs to be changed more frequently. They actually had some engine failures because people were not changing thier oil until around 12 - 20K! He recommended I change my oil between 5 - 8K to be safe. You see the 6.4 actually produces oil by allowing fuel to flow into the oil, thus producing more oil than the original 15 quarts you installed! Therefore, common sense will tell you, just run a good conventional proven oil like Shell Rotella T or something comparable; save yourself $44 since you have to change it more frequently anyway! Just my 2 cents worth of advice!
