I have an "06" Duramax my 3rd oil change (around the 15k mark) was to Rotella full sythetic. im at 55,000ish now and think the oil is great. the thing thats important about an oil is how it handles contaminates. being a diesel engine your going to get soot in your oil. if im not mistaken rotella is designed and manufactured with soot contamination in mind and is formulated to deal with that without as much chemical side effects as other oils may have. mobile 1 is a great oil and i run it in all my gas engine vehicles but i would run rotella synthetic over mobile 1 in a diesel. ive changed alot of oil in alot of road tractors and almost 100% of what i put into those tractors was rotella. and 100% of what we put in our fleet of western stars was rotella synthetic.
2006 Silverado crew cab 2500HD Duramax LBZ, Allison 1000, BD Full bore exhaust manifold, Diamond eye downpipe-back 4" exhaust, Bullydog PMT tuner, S&B intake, Golden fuel systems SVO conversion. Heavy right foot.