Find the person who told you never to use Rotella in a 6.0. Take a picture of him and write down his address so you never forget him. Now, run Forrest, run away from that evil stupid man!

Mobil 1 for Turbo Diesel Trucks is a fine oil as is Shell Rotella T6. I used TDT back when it was the same formula as Mobil Delvac 1.

Delvac 1 is probably the best diesel engine oil, but it's expensive. I consider Mobil 1 for turbo diesel trucks and Shell Rotella functionally equivalent. Both show excellent performance in 6.0 engines. You can buy a gallon of T6 at Walmart for $20.56.

I don't use Delvac 1 simply because running extended oil change is a really poor idea. Group IV synthetics like Delvac 1 make economic sense for long change intervals. Less expensive Group III + oils like TDT and T6 give you the cold start / cold weather benefits and w40 high temperature performance without the extra cost of a long oil change interval Group IV oil being dumped every 5,000 or 7,500 miles.