Keep in mind that if you are like most people on this board you will not be waiting 5-7k miles between
oil changes. Im no expert but any of the good 15w40 diesel motor oils should work well. Mobil 1, Castrol, Rotella, all would be fine choices. I run Castrol, if anyone has information that I should be running something else or that there is something wrong with the Castrol 15w40 please let me know.