I agree with the previous poster, over filling could be a problem. Too
much oil may be getting kicked up onto the cylinder walls by the
crankshaft. Too much oil could be overloading the oil wiper ring.
If the oil level is good, watch the oil level. If you're burning oil,
your oil lever will start dropping. If there's no change, then assume
it's fuel related.
Are you sure you put in the right oil? If it's a lighter weight oil,
can it be getting past the rings?
I can't imagine that a cummins with only 100,000 miles on it will have
work rings or valve guides.