It's Heavy Duty extra high performance Diesel engine oil provides : Extra engine efficiency thanks to an outstanding soot dispersancy and control. Prolongation of engine life thanks to an excellent thermal and oxidation stability. Extended drain intervals thanks to an excellent TBN retention. If you have mixed fleets of different engine designs, by using ELF PERFO HDX 900, you will reduce your maintenance and inventory costs allowing fewer oils to be stored and reducing the chance of problems arising through product misapplication.