ISX Oil in Coolant

[inmsa]

Good day guys, we bought a ISX CM871 2008 Pete with arouund 800k miles, we did all EGR, DPF, Coolant, valve clearance, injector and oil maintenance recently and we came into a problem where we found Oil in coolant, we haven't made the pressure test, but our oil level is not going down noticeably (we will start to monitor this more intensively). Can you share your thoughts on this problem? Would it be oil cooler? Oil has not shown any signs of coolant mixed with it. Is EGR Cooler connected to some oil Lines that we are not aware of? From earlier inspection we have a good EGR Cooler. And we are thinking of a EGR delete, is EGR Cooler needed after EGR delete has been done? We have no problem with any regulations.

FYI Oil came out very dirty on first oil change and got dirty very fast, to the point that we had to change an oil filter during the first 500 operating miles, we used fresh Delo 85w90 or 140 I think, I'll have to confirm tomorrow. Is this normal due to build up inside the Engine?

Thanks please advise.