I am 100% certain that Amsoil TBN is 12+ for the HDD 5w30. It is also 12+ for the 15w40 and 10w40. Confirmed by amsoil spec sheets AND baseline analysis.

Most agree that soot can go to 3% before one needs to worry - this is true for CH-4 rated oils which are the majority of diesel oils. With older CF oils (non-diesel synthetic oils Mobil 1, Valvoline SynPower, ...) I might stick closer to 1%.

Brian