guys you can't judge diesel oil by it's color. Gasoline engines will stay gold for awhile because of their lower compression and ring design. Diesel oil can still be perfectly healthy and very clean while still looking jet black.
Find a Cat dealer... They will send you the SOS bottles, a mailer, and run the analysis for you. They ONLY way to tell if your oil is healthy is with SOS.
Wear metals can be present that you never knew about, high soot levels, low TBN, low viscosity etc. SOS will show you everything that's going on with your motor, and often enough it will tell you when something is going wrong, and what part of the motor is having the issue.