Not sure upon what you based your answer but you may be right. However, ordinary 10-40 and 20-50 oil lists API service of either SH/CD or SJ while
15-40 oil lists API service classifications of CI-4, CI-4 Plus, CS-4, CF-4, DF/SL and SJ. This is service recommended by Catipillar, Cummings, Mercedes-Benz, etc.