That said, there was one thing that really made me want to get a car, just so I could try it. It was this simple modification that you can perform on your car to turn it into a vegetable oil powered "greasecar": http://www.greasecar.com/
The one catch, though, is that your vehicle needs to be a diesel powered car or truck.
Through the website, you can essentially purchase a conversion kit, which essentially comes with a heated oil tank and all the necessary hoses and wires to make your car stop running from your normal diesel tank and start running using vegetable oil in your heated oil tank. From what I understand, once you install the kit on your car, you'll only need regular diesel to turn on the car. Once the car is on, the heat from engine gets transferred to the heated oil tank, so that the vegetable oil gets heated up enough to have a similar consistency to diesel. The vegetable oil is then injected into the engine similar to diesel and the car runs using the vegetable oil.
The major benefits from using this vegetable oil system are that it is carbon neutral, it doesn't wear away the engine very much, has similar fuel economy to traditional diesel engines (diesel engines have better fuel economy than gasoline engines anyway, so it is certainly a benefit over traditional gasoline powered cars), and you can probably get vegetable oil for free from restaurants which would have to throw away their oil normally - just make sure that there is no water or potential bacterial contamination in the oil, which could mean bad news for the emissions and the vegetable oil system.
You can find out more about the Greasecar Fuel System here: http://www.greasecar.com/faq.cfm, and if you're interested in converting your car into a Vegetable-Oil powered car, you can purchase kits here: http://www.greasecar.com/product_list.cfm?cat=Greasecar%20Kits