biodiesel vs. straight vegetable oil (SVO)
I'm no expert, but thought this might help some people...
Biodiesel is not vegetable oil, it's a fuel made from vegetable oil.
There's lots of info available on the 'net on biodiesel and vegetable oil, if you feel like doing a little research. Veggie oil is usually referred to as SVO (straight vegetable oil).
A diesel engine can burn either, but both require some mods, for biodiesel PTJudeRI's post is accurate as far as I know, and for running SVO, I think much more extensive mods are required, especially to provide a system to heat the fuel in the tank and the fuel lines to liquify the veggie oil and prevent it from coagulating on it's way to the engine.
Anyway, like I said, I'm no expert, I just wanted to the make the point that Biodiesel and SVO are two different things, and that there's plenty of info available on both on the 'net, so if you are interested, hit google and read up.