CJ-4 has reduced TBN, ash content and ZDDP versus CI-4+ in order to protect exhaust aftertreatment devices like particulate filters and catalytic converters.
Reduced ZDDP (about a 15% reduction to 1200 ppm which is still pretty healthy) reduces one of the better anti-wear additives and anti-oxidants (prevents thickening of oil at high temperatures but to an extent it has been replaced by other additives.
Reduced TBN is due to a reduction in calcium detergents (calcium sulfonate) and certain other additives, which means the oil may not have as long of service life as CI-4+ rated HDEO. ULSD has helped with this to an extent though, as it does not form as many acidic byproducts from blowby, helping to protect the oil.
Both are part of the reduction in sulfated ash overall to 1%, as any oil and additive consumed is hard on those aftertreatment devices that the manufacturer must back for an EPA mandated amount of time.
ULSD is somewhat harder on injectors, fuel pumps and upper cylinders beacuse of reduced lubricity but those paying enough attention to keeping them on the road for a long time were likely running something like Lucas UCL already. I don't think they intended to wipe them out and slow wear is a pretty long term way to do it.
