Great info guys, your input is valuable and I appreciate your input. It seems that Mobile One oils for diesels would have to be pretty good oil. Other than a quart or two, my supply of Shell Rotella 15w-40 is almost depleted. I think when I do my next oil change I will make a switch to the Mobile One Delvac 1300 Super oil. I really don't drive enough miles in a year to justify using a synthetic oil so I will stick to the Dino oil.I used to use Shell Rotella when my truck was new. I had a couple of "Iffy" Oil Analysis results. I switched to Chevron Delo 15W-40 and Mobil Delvac 15W-40 and got better UOA's back from Blackstone Labs. I now use Mobil 1 Synthetic 5W-40. I feel more comfortable using Mobil 1 and Chevron Delo. Just me being quirky.