What type (weight) of engine oil to use its a diesel
Thanks
API classification diesel oil (CJ orCI, what ever the latest is) SAE 15W40 works for most diesels in ambient temperatures above ~32F.
Some CJ oils are not backwards compatible to the CI-4 spec and are intended for Tier IV compliant engines only.
The API data in the post below yousr says that CJ's are backward compatible if used with ULSD fuels.