Here's some terms that you should know:
Bio-Diesel -- This is a
type of fuel made from vegetable oil. It involves a chemical process
called transesterification, that removes the glycerin from veggie
oil, and replaces it with an alcohol. this fuel can be poured directly
into the fuel tank on any diesel vehicle, and run without any modifaction
to the vehicle.
Straight vegetable oil (SVO) -- This is the term describing
any veggie powered vehicle that is running on only veggie oil. The
oil has not been processed in any way, and has to be heated before
it enters the engine.
Waste vegetable oil (WVO) or
"Grease" -- This is any
veggie oil thathas been used for cooking, and is now being recycled.
It can either be made into bio-diesel, or run as straight veggie
oil.