MPG on vegetable oil

I'm doing a big essay for school on ease and costs of using vegetable fuels and was wondering what the typical mpg is on a vehicle running on straight veggie oil using a convertor. I want to compare costs since veggie oil is about 9$ a gallon. I'm 16 and am also interested in using this method when I buy my dad's car :D

Any help is greatly appreciated!

Reply to this post

Image CAPTCHA
Enter the characters shown in the image.