Driving a diesel vehicle on ordinary vegetable oil is not only possible - I've been doing it for years!
However, it's a big topic, too big for a few pages sidelined on this website. As such I have a website dedicated entirely to the subject.
To visit my VegOilCar website, click the image above or use this link.
There you'll find answers to your veg oil motoring questions as well as the very real story of how I converted my Toyota Landcruiser to run on pure vegetable oil, the same sort of stuff you'd fry your chips in.