Heck they don't get broken in until 100,000 miles so what's the use. Been using dino for 490,000 + miles with no problems... is purely a peresonal choice.
I don't understand that. We spend 40K on a truck and then won't spend a few more bucks a gallon for top shelf lube? I like Rotella and dino oils like it. They are good product but they are not in the same league as a quality synthetic. Very good but not that good.
Putting synthetic oil in a diesel motor is a joke. Especially a cummins diesel. You run the risk of offending it, to the point of it not cranking on occasion. :-laf
We put John Deere oil in all our cummins "vehicle" engines, and NAPA in all the "stationary" units. They break down sometimes, but never because of the oil.