I'm a new owner of a 4520m. The tractor comes with a soot level indicator on the display, and an automatic exhaust filer cleaning system. I've been slowly watching the soot level build up to the point that it is now reading 66% (only 25 hours on the tractor). The owner's manual says that the automatic system continuously cleans the exhaust filer, hence, I wouldn't think the soot level would get this high and continue to climb. Can anyone help me out here? There is little to no other information in the owner's manual.