Not true. The CJ-4 oils are a compromise to allow particulate exhaust filter equipped vehicles meet emissions. CI-4+ oils have better (heavier) base stocks (higher TBN number on analysis) than CI-4 oils. If you don't have a particulate exhaust filter (Cummins 6.7 has them, 5.9 trucks don't) then you are getting a better oil if you can find CI-4 grade. Manufacturers just say that they are backwards compatible (which they are, but not the same durability of oil base stocks) because they don't want you to avoid their product. TDR did a comparision on CJ-4 oils and CI-4 oils, and while they are compatible, they are not equal at this point. This is why AMSOIL continues to produce CI-4+ and CJ-4 oils separately. The better base stocks in CI-4+ oils allow longer drain intervals that the CJ-4 oils cannot.
And just a couple things...it is correct, CJ-4 is backwards compatible, but that doesn't mean it is the same or similar as CI-4.
The TDR article has been under A LOT of criticism on TDR...most are saying the only thing it compared was VOA (virgin oil analyses), and while the "expert" was able to pick out the CJ-4 oils, it only means the oils are different, has no bearing on ANY of the actual oils' performance...I mean, come on Chuck, they rated Amsoil low (do you think that was a realistic opinion?).
And further, WE DO NOT KNOW how the CJ-4 oils are going to hold up. For those of us doing the recommended OCI (15k or less), there will be no issues (based on current UOAs of CJ-4 Rotella).
As I noted on TDR, we are still in the "old school" oil analysis phase...these newer oils might have components that a normal UOA/VOA wouldn't necessarily show. I'm sure some of Amsoil's proprietary stuff doesn't show in a typical UOA... And because of this potential discrepency, the CJ-4 oils may perform just as well as the older CI-4s, but might not show it in a VOA.
And Chuck, one of the "marketing points" of CJ-4 Rotella is the fact they changed to a better base stock (Group III?) compared to CI-4. Just FYI...