Synthetic oil is great stuff but there is nothing wrong with running dino. (Shell Rotella, Chevron Delo or Mobil Delvac) Diesel engines have been around a lot longer than synthetic oil and there are tractors from the '40s and '50s still chugging along on Dino oil. If you use dino oil, you just have to change it more often. I run all three dino oils in my four diesels and they all run great. (usually Rotella)

The only special case where I would use synthetic oil with a premium oil filter is if I was towing big loads over long distance with my Cummins 6BT. In that case, I would be running AMSOIL and a premium filter like Fleetguard/Mopar, etc. with extended oil change intervals recommended by AMSOIL.

Pmontero

P.S. - I'm not an AMSOIL dealer and have no affiliation with them. I just know a lot of diesel truckers that swear by it.