I am running Delvac 1 ESP 5w40 CJ-4 in my 2008 Dodge 3500 Cummins. The truck will pull 10-14,000 pounds continuosly. I plan on doing UOA's but at what mileage should I pull a sample and how long do you think I can safely go? I have chosen this oil because I spoke with Doug Hilary about my concerns with the diesel particulate filter and EGR that this engine (and all newer light diesel trucks) has. This truck needs to remain reliable so I do not want to "chance" an emisson related breakdown.