It is a Group III, but a different process as I understand than the Chevron one. Suppose to yield a very good base oil with excellent cold flow properties.
Well known fact that the Rotella T 5w40 is a Group III. It is produced from a different process than traditional group III's however. Essentially, it is similar to the process that produces Group IV PAO's, but uses a different feedstock (slack wax) instead of other gases.