Common practice is an amazingly local thing. Typically a plant or facility will refer to product in the same terms as the sales contract at that facility. Many localities sell liquids by weight and use mass terminology, others use volume terms and correct to a specified temperature. I see bulk oil in mt pretty often associated with ship loading/unloading facilities.
I work all over the world and it always amazes me when I meet someone my age who has only worked at one facility for an entire career. These are the guys that truly believe that the way things are done within that one plant were ordained by a higher power and everyone else either does it the same way or is wrong. If the facility sells liquids by tonne, then they will argue that there is no way to get accurate volume measurement without knowing the weight and density. If the facility sells liquids by the m^3 then they will contend that inherent errors in weight instruments make volume the only valid way to assess a quantity in liquids. They are both wrong, but will not be convinced that there is validity to another method. It makes the life of a consultant interesting.
David