I like the waste oil route. Thinking of getting on from Northerntool.com
http://www.northerntool.com/webapp/w...6&categoryId=0 Cheaper than others I have seen and enough heat for a small shop or garage. Best of all it gets rid of the excess waste oil, not just motor oil but gear and tranny oils too.
Also some cheap, do-it-yourself kits or plans.
Brandon
Olympia, WA
http://journeytoforever.org/biofuel_...earth/me4.html
http://www.heco.net/Wasteoil.htm