I remember an old episode of Top Gear. Jeremy Clarkson was testing a diesel car to see if the cooking oil story was an urban legend. He had someone filter enough used cooking oil to get the car running and the engine started up. Now considering that pranks always abound on the show, I don't know if it was for real. (Hey, his crazy co-host James May sabotaged his RV in one episode!) Has anyone tried running a diesel with cooking oil? Do you have to mix it with some diesel fuel to make it work?