Last change for my 2006 GMC Sierra diesel was in July 2016, I'll hold off changing it again until the oil analysis recommends another change. Using Amsoil Series 3000 5W-30 HD Diesel Oil (recommended for pre-2007 diesel engines), with an Amsoil Remote Dual Bypass Filter System. Tested every 7,500 miles and never once had a report that even came close to recommending an oil change. The dual filter with a high efficiency bypass filter changed every 50k miles, or upon second primary full flow filter change every 25k miles, keeps the oil clean. Even soot contamination after 21,000+ miles remains under .1 of 1 % of volume, same for oil fuel dilution, and viscosity thinning from sheer. The additive anti-wear metals always remain well above minimum concentration, and the viscosity remains constant. While the DuraMax engine is thrifty on oil consumption, the small amount of makeup oil replenishes the additives sufficiently to maintain viability. Given the new oil required at filter changes, I may never have to change the entire fill of 10 quarts + 2 quarts for the filters, again. Given that I keep the extended warranty current, maintaining used oil analysis records is required should anything go amiss.
I also run a Baldwin coolant bypass filter along with Amsoil Propylene Glycol Antifreeze & Coolant, to protect the cooling system. After the first annual filter change I found the filter media had trapped considerable residue of engine block casting sand, scale and what appeared to be flecks of gasket sealer. The filter will also trap any products of coolant breakdown, that white concretion that plugs radiator tubes causing overheating, This coolant is rated 150k miles or 5 years in light vehicle applications or 600K miles 12k hours or 6 years in heavy duty applications.
