Backward compatible:
PC-11A (Licenses as API CK-4)
- Viscosity grades include both SAExW-40 and xW -30 engine oils with >3.5 cP HT/HS viscosity
- Backward compatible with previous categories: including API CJ-4, CI-4 Plus & CI-4
- Higher level of wear and oxidation protection versus API CJ-4 oils
Source and overview here: What is Diesel Engine Oil Standard PC-11 | Chevron Delo PC-11 (http://www.pc-11explained.com/pc-11-explained.html)