What is the highest grade model for diesel engine oil?

[NicoleRose]

The highest grade for diesel engine oil is CJ-4. The grades of diesel engine oil are roughly categorized as: CA, CB, CC, CD, CE, CF, CF-4, CG-4, CH-4, CI-4, CJ-4. Different models of diesel engine oil grades indicate varying oil grade levels and corresponding applicable vehicle types, meaning the further the letters are in the sequence, the higher the oil quality grade, and so on. API engine oils are divided into two categories: "S" series: The "S" series represents oils for gasoline engines, with specifications including: API SA, SB, SC, SD, SE, SF, SG, SH, SJ, SL, SM, SN. "C" series: The "C" series represents oils for diesel engines. When both "S" and "C" letters are present, it indicates that the oil is suitable for both gasoline and diesel engines. The SN grade is currently the highest grade of oil. SJ was the standard in the 1990s, SL was the standard in 2001, SM was the standard in 2004, and SN was the standard in 2010.