This group is for vehicles that run directly off vegetable oil (aka: vov, grease car, greasecar, wvo, waste vegetable oil, svo, straight vegetable oil). A petition process is used to block spammers.

A diesel vehicle is converted using a "kit", to start on diesel, then after it is warm, it is switched from diesel to run directly off vegetable oil. Conversion kits can be purchased from a few companies, one of which is developing more "maintenence free" system.
Sources for vegetable oil are fast food, Asian, or middle eastern resturants that use vegetable oil to fry food. It is generally a good idea to contact target sources for waste vegetable oil and create an arrangement so you can call ahead to pick it up. Its good for them because they usually have to pay to get rid of their waste vegetable oil. The oil is filtered to remove contaminants, and then put in a separate tank in the converted vehicle.

This group is not for bio-diesel which is different and there are plenty of biodiesel discussion groups.