I have a new to me 2004 LB7 with 135,000 miles. Upon any type of heavy acceleration I get black smoke. Similar to when I had a built 6.5. The oil pressure also drops from 60 psi to 30 while cursing to just above the red while idling. The oil hasn't risen and does not smell like fuel. It smokes black when pulling a 4500 pound trailer up a hill and seems to load up.
I get 19-20 mpg while cursing at 70 mph.
Is this normal?