Going through youtube videos I fell on this interesting explaination of Vegetable Oil Engines. It convinced me that it is very possible to do this on your own with little knowledge about the technique. Wikipedia has more about this topic. I think that the only thing that they do not mention in the video is that the veggie oil will have a little bit of an odd scent, but its always better than gasoline which you know pollutes your lungs and the ozone. Better stink than sick ! VIDEO->
The video is from treehugger.com but I have no direct link to their Veggie Oil Engine page.