A good reason to disable the EGR is to keep diesel exhaust gasses, soot, and particulates out of our intake systems. Those particulates cannot be doing anything positive to the cylinder walls, valves, intake manifold, or oil.

I'm currently "offroad testing" my CDI with the EGR disabled. I'm anxious to see what the oil looks like after several thousand miles compared to the black color I saw previously in just a few hundred miles.

If chronometers EGR valve was caked with soot, one has to wonder what the rest of the intake tract looks like?