Another factor in the petrol vs diesel equation is the annual tax. In Australia there is no difference in the annual registration fee between petrol & diesel cars. In most european countries there is an extra annual tax on diesel vehicles. For example I pay an extra 560 euro per year on a 99 passat tdi wagon, compared to a petrol passat wagon. The prices at the pumps are 1.05 euro per litre for diesel, 1.35 euro per litre for 95 octane petrol.

Crunching the numbers, if you do more than around 15,000km per year here it's better to have a diesel. Also diesels have a much stronger resale here. About 30% of all new car sales are diesel, around 50% for VW/Audi.

By the way you can buy biodiesel in Australia, the price is $1.27 per litre. Here is the link:

http://www.northcoastbiodiesel.com

In Sydney you can buy it at the BioDiesel station on Marrickville Rd, Marrickville.