The current word about fuels in Australia goes like this.
Shell - decent fuel and has a cetane number of 49 in Australia. It's pure dinosaur.
Mobil (from Mobil) - same as Shell. Mobil sells both dinosaur and biodiesel but I haven't heard of any pure biodiesel sold to the general public.
Caltex - 51 cetane, so a little better than Shell. Has detergents and possibly anti-foaming agent added. Caltex will (depending on area, availability etc) mix up to 5% biodiesel. I heard somewhere that it's typically around 2% on average but might sometimes be as high as 5%.
BP has two flavours: Diesel and "Ultimate Diesel". The former is 51 cetane with detergents and anti-foaming agent. The latter is 55 cetane with detergents and anti-foaming agents. It's also pure dinosaur.
Others (7-Eleven, United, Metro, Liberty etc) are usually supplied by Mobil but there's a rumour (and this one can't easily be proven) that the tanker drivers mix it at up to 20% biodiesel before delivery. I'm not sure about Gull.
All diesel fuels in Australia have to be "ULS" (Ultra Low Sulphur) with less than 10 ppm of sulphur. This is not a cheap process - removing more of the sulphur makes the fuel more expensive. There is NO sulphur in biodiesel though - and commercially produced biodiesel is supposed to have a higher cetane number than dinosaur. Some experiences with biodiesel attribute poor economy and performance to it, although my own experience with a mix of fuel obtained at Kings Creek Station (Mobil products, likely to have 20% bio in it) was far more positive.