Last week I was in O'Reillys - here in Cheney, WA - buying windshield washer fluid. They had T4 and T6. I don't know about the local NAPA store. I don't use synthetic in my
M6040 - a waste of money. Now my new Ram 2500 Power Wagon uses 5W40 full synthetic. I purchased the lifetime oil change option with the PW. So....oil changes are done at the dealership.
I wonder - can O'Reillys still get Rotella or do they just have a large stock pile of it.
Your owners manual will suggest oils by specs not brands. Go with that........