i dunno what hemp seed oil is, but biodiesel can be made from just about any kind of vegetable made oil. ie peanut oil, vegetable oil, soy oil, etc...
Ihad a buddy that did this, he swore by it as well, and always cracked up when people said his truck smelled like french fries, or chinese food, or hash browns, or whatever oil he happened to have in it at the time
