You should research the new CK4 spec. It has ISB specific tests regarding tappet weight loss and cam lobe wear that CI4 oils were not required to test for. There's also 3 or 4 ISM specific tests required to meet the spec. Real world results has shown the current oil specs are indeed more than capable over the last 13+ years. Oil change intervals have literally doubled if not tripled compared to the CI4 days, and that's with the introduction of EGR no less. Largely due to the performance of the new oils. Fleet owners with dozens if not hundreds of trucks run fleet spec oils such as Mobil Delvac or Rotella T3, economical entry level bargain oils with good results. Oil related failures are all but unheard of, I wouldn't hesitate to run any of the big name companies. They've all accumulated millions of miles of testing before CK4 was even released and can be had fairly reasonable if you look for the sales. Tractor Supply has a sale on 5 gallon pales of both T4 and Delo 400 right now at $60. I've seen them even cheaper with manufacturer rebates from time to time.