You know what Paul? My first oil change was done at 1.200km at the dealer. Because he told me to do so. ("Bring the scooter in at approx. 1.000km...") They refilled and overfilled with 1 Liter of unknown dutch semisynthetic 10W-40 Oil...
My second oil change I did myself at approx. 5.000km and switched to Castrol high end fullsynth oil 10W-40. And my third oil change will be at 10.000km (still 700km to go). Very happy with the scooter and no complaints. But it does consume a little bit of oil per 1000km (~ 0.2L). But I ride all kind of roads, also Free- and Highways full Throttle.
For moderate climate zones a 10W-40 should be good enough. For hotter climate zones like your Down under, I would suggest that a 50 Grade Oil is better in summer. So a 5W-50 should be perfect for you throughout the whole year. Bear in mind, that the quality of an oil is also determined by the API Rating (written on the backside of the oil bottle). An API Rating from SJ (minimum requirement) onwards (SL, SM, SN) is just fine.
Modern good quality Motoroils should be able to make 5.000km - easily.
And the reason why I use full synthetic engine oil is, because I think that this oil keeps the engine and itself cleaner over a longer period. The gulp of fresh oil every 1000km also kind of helps to keep the oil within specs and is not a problem for me so far.
