I use only Caltex (not woolies/caltex) fuel. Either Unleaded or Premium. Same for boat and car. No problems and have been using ONLY caltex for 5 years (fuel card).
I'm not sure if the performance / efficiency gain on premium is only psychological, but I like thinking my car/boat is feeding on the good stuff. I would only use premium about 5-10% of the time though.