Guys - rather than modifying the oil to run in a standrad car, modify the car to take to oil. Considerably cheaper and safer that making biodiesel at home! (The orginal diesel engine was actually designed to run on peanut oil - 'turning the clock back' so to speak on a modern diesel isn't as complex as it sounds. With a bit of care, used cooking oils can be prepared in a low cost & simple way for us in a converted car.

Check out www.smartveg.com (and www.regenatec.com)