The fat, or tallow, from one poor deceased sheep will produce about eight litres of biodiesel.
That's about 6 1/2 sheep to fill the tank of Holden's Astra diesel hatchback, meaning you'll get about 105km out of one animal on Holden's published fuel economy figures.
Pigs are better for travelling longer distances, with one unfortunate beast giving Astra drivers about 140km. "This is pushing biodiesel to a whole new level.