Has to do with the cross hatching of the cylinder
I guess cylinder washing occurs.
Cross Hatching>>Pattern placed upon cylinder walls during manufacture/overhaul to ensure proper oiling of rings during break-in...run-in.
Cylinder Washing>>Incomplete fuel burn during Cold OR hot operation due to any reason..from bad injectors, uneven fuel feed, etc. GAS or Diesel.
Just want to clear that up,
Hope this Helps,
CF