I did a bit of a comparison of my own. i normally use Penrite oils, but decided to try a Nullon semi-synthetic oil in the VS Commodore with the 3.8L V6. The first impression was a slightly quieter engine operation, particularily with the pushrods and tappets. As an Australian manufactured oil product, it is up there with the best of them.
Australian manufactured, better than expected quality.
Little pricey, more brand awareness needed.