Coolant in oil (Oil analysis)

[Hammerhead]

List of possible coolant intrusion points of oil in an ISX CM871.
no particular order, or complete
EGR cooler
Oil cooler
Liners shifting/rocking/dropping
Head gasket
Cracked head
O-rings on liners
Cracked block
VGT turbo
Water pump
Air compressor

Do a coolant system pressure test and investigate from there. Pressurize to 20psi, overnight if you can't find it immediately.

Most likely culperit is EGR cooler. Pressurize cooling system and remove the crossover pipe at the rear and use a mirror to verify. If not, further investigation will be required.

As far as severity, that's determined what the issue is and the coolant consumption rate. Coolant is abraisive, not a lubricant. It also attracts soot, making it even more abraisive. Depending on the issue, this may require an inframe in short order to being able to limp it for several months to save your pesos to do so if it's not a simple components replacement.