The 6.6L direct injection gas engines in the HD trucks are an unknown commodity as far as carbon build on the valves, etc. There is no longer any fuel wash to help keep the valves clean over time and it is well documented, from other brands, that the carbon build-up can get quite severe using direct injection. Part of the Dexos 2 oil design specifications are to primarily control the residues from oil vapor, blow by and build up in the intake tract. I plan on 4500-5000 mile oil change intervals with Shell Rotella Gas & Truck 5W30 and Baldwin B7449 filters. I’m in FL and the oils look like ice tea when in operation in the heat. Oil and filters are cheap when you consider most have a $70K + investment!!!
As they say: “You pays your money and You takes your chances”!