Mobil Delvac 1300 Super 15W40 CK4/SN
I understand the factory oil fill in the Duramax is still Mobil Delvac 1300 Super 15W40. Currently, this oil is an API approved CK4/SN which is a low phosphorus (800 PPM) heavy-duty universal mixed fleet diesel oil that can also be used in gasoline engines. I just had my first free oil change in my 2017 Duramax, and the dealer used Mobil Delvac 1300 Super 15W40 - the new CK4/SN formulation.
The previous generation of Delvac CJ4 HDEO performed well in my 04 Duramax, and I used Delvac successfully for many years. However, I have not seen any used oil analyses (UOAs) on the new CK4/ SN Delvac 1300 Super 15W40. I am curious how the current CK4/SN formulation is performing in the Duramax, especially considering the lower level of phosphorus.
Any feedback on the performance of Mobil Delvac 1300 Super 15W40 CK4/SN would be appreciated.