As the school year wraps up, I've had a lot of questions from people with plans to buy and convert a Volkswagen TDI to run on vegetable oil. Here's some good information: The normal price range for a decent TDI is $5,000 to $10,000. They are a little pricey because they last a long time and are in high demand. Don't bother going to the dealership to find one. They will all be gone, and the ones you do find are going to be overpriced. Volkswagen of America has set about buying back TDIs from previous customers, for full market price, so they can keep TDIs on the lot. Thus they are selling them above market price. Your best bet is private sale. Watch the local classifieds like a hawk. In vermont, I would check Burlington Free Press (also listed in cars.com ) and Motor Digest. Don't be in a hurry- it may take a month or two. Check out everyone you see. Find out if the timing belt has been changed, and adjust the value accordingly. It's a pricey ($800-$1000)