6.0? You have a fuel injector problem. You have a fuel injector that is dumping fuel into the oil, either by dumping it into the cylinder and past the rings or up through the top of the injector past some torn o-rings, and the compression is likely leaking past the injector, into the fuel system, which is why it's shutting down. There's a copper o-ring/seal at the bottom of the injector that seals against compression, when they fail, compression gets pushed into the high pressure fuel system and then it can't pump fuel. That copper o-ring/seal seats against a copper "injector cup" in the head, if that's damaged it'll need to be replaced as well. Low fuel pressure is the biggest cause of damage to fuel injectors, if you haven't had it done already there's an upgraded spring for the fuel pressure regulator. Also, there's a fuel injector control module that jumps up the 12V system to 48V for the injectors, when they fail and start making less than 48V that's also hard on injectors and they need to be replaced, There were plenty of trucks back in the day that got all 8 injectors, the upgraded spring, fuel filters, a FICM, and an oil change.

Diesels are never cheap to repair.

It's a 6.7L . It does not have fuel in the oil, just over full. Not smoking.

how overfull with oil ?

you your thinking well I put 1-2 more quarts in than I should have and they are draining 7 extra out then not your issue and probably is fuel.

What year?
The early ones had two piece glowplug that would separate and go into the cylinder, wrecking cylinder.