I'll give you some things to ponder. It's not that I'm right and you're wrong, but more just points to mull over before your decision.
I see plenty of evidence that CJ-4 protects against wear as well as it's predecessors. Plenty of UOA evidence there. The data is stacking up every day that show CJ-4 oils can product wear rates as low as, if not better than, the preceeding products.
You do loose some TBN with CJ-4. This could have an adverse affect only if you run LSD fuel, as you'd have to keep an eye on the TBN. But since most people OCI way before oil is used up, it's a moot point. If you're running ULSD fuel (which nearly everyone is) then the lower TBN of CJ-4 means nothing in the debate.
One avenue where CJ-4 far surpasses even CI-4+ is soot control. The new DPF equipped vehicles have the most EGR and after-combustion regen cycles the market has ever known. The soot load is now higher than it's ever been. CJ-4 oils were designed for this very task. The detergent and anti-agglomerate (dispersent) package is extremely robust. Further, because of the greater use of EGR in the new vehicles, the EGT also is higher than older vehicles. The CJ-4 oils have been tailored to have more evaporation resistance; it is suspected by some of us that the base stocks have been upgraded, even in dino oils, to help combat this added heat load.
If you combine ULSD fuel (lower need for TBN) with the soot and heat control abilitiles of CJ-4, in a pre-DPF vehicle (no regen - such as your ISB), then you have the best of both worlds!
I'm not saying CI-4+ is bad stuff; quite the contrary. But CJ-4 doesn't need the TBN because there is way less sulphur. The loss of some portions of the add-pack are perceived as "bad", but in reality ULSD negates that problem. Then consider the much stronger soot control package with CJ-4, and what's not to like?
If you could get CI-4+ as some screaming deal, I'd say go for it. Otherwise, CJ-4 fluids will do just fine by your ISB.
