Used motor oil ??

Burning waste oil can be very very dangerious and can hurt mother earth. Now that that is said, you can use this for heat if you do a little work and not hurt the world.

If you have a brick lined heater you can make a inprovised blast furnace.
This thing will get HOT.

I know of two people that have used these. They work very well. The only draw back is the sound.

http://www.backyardmetalcasting.com/index.html

Old information, but sound.

Whip