Just bought a 2012 2500HD with a 6.0L. Looking through the owner's manual, it states use Dexos1 approved oils...that really limits the oil you can use. Several name brand options I would use are not on the "approved" list, although I would hazard a guess they meet or exceed because they met the older GM specifications. The 2011s state you can use an API rated oil in substitution, but no mention of that for a 2012. GM is charging $0.09/quart of oil for the Dexos1 approval...so we are paying GM for an oil they approve? Sounds like just another way they can generate income? How many actually pay attention to the Dexos rating and just run a quality oil?