10K miles is a good number for a relatively lightly driven Duramax. A hard working Duramax might need it a little sooner. I go by how dark the oil gets over time. The 6.2/6.5, on the other hand, need to have their oil changed about every 3k miles (gets darker sooner).



This is a pic of a Ford Powerstroke (either a 6.4 or 6.7) that failed due to not changing the oil. An expensive lesson... The twin turbos had failed as well. The pic shows the top of the cylinder heads with the valve covers removed. Looks like you sprayed on a heavy coat of bedliner on all those delicate parts...