Use any good grade diesel rated oil that is correct for your climate / temperature range.
That's probably gonna be a 15w40 or a 30w/40w (winter/summer) for the bulk of america.. and most tractors new and old.
15/40 has been specced in jap built engines in its compacts since at least the early 90's as well as in the larger units.. like my 7610. My old tractors got 30 and 40 wt oil.. etc.
Soundguy