Just having some fun I came across that website and thought I could generate a little controversy and other assorted WTF reactions ! It would be interesting to try with an old rabbit diesel or some other such car . By the way , on Mythbusters the other night , they used an older Mercedes diesel that got 33mpg on diesel to try this on . They used actual unrefined used french fry grease and the car got 30 mpg . Not bad for something you'd throw out .