I have a NH TC 30. Bought it used but in great shape with only 600 hours. Time to change the oil. Can I use "motor oil", or do I need to use a special oil for diesel engines?
Welcome to TBN.
Ideally you would use a high quality synthetic or semi-synthetic DIESEL oil rated to the tractor's specs for grade.
Mobil one diesel, Amsoil diesel, etc.
You need C rated oil, not sure what API rating there up to now CG?? But yes its a diesel rated oil, use what ever rated oil the manual says like 15w-40 or 10-40 or what ever. MOst use Mobile delvac, dello, rotella T, or some syn oil.
Diesel oil is different, it is formulated to hold ash and soot in it in suspension.