Bill,
Welcome to the forum.
In general, biodiesel has around 5% less energy than petroleum biesel. This translates to around a 3% reduction in fuel economy.
If you use B20 biodiesel (20%Biodiesel, 80% petroleum diesel), I would not expect any noticable change in performance or economy. The only thing to watch, would be the possibility of the fuel filter clogging. This would not normally be an issue with B20 as long as the fuel filter were changed at each service interval.
If you were to use B100 (100% biodiesel) I would expect a barely noticable loss in power and a slight loss of economy. I would also carry spare fuel filters as the 100% biodiesel will dislodge the sediment of years of petroleum diesel use and send it to the fuel filter. After 2 - 5 tanks of B100, you should be past the filter clogging stage.

After the tank has been cleaned by the biodiesel, there should be no problems switching between petroleum diesel and biodiesel.

There is a "Biodiesel Finder" link at the top of the page here which will show a map of Oz, showing the locations of known biodiesel outlets. Clicking on the "Show Full Details" link will display the address and the biodiesel blends available at that location.

If you locate a Biodieel outlet which is not shown on our map, please bring back the information to allow our map to be updated.

Regards,
Tony