I have what I think is a good design waste oil heater that has been heating my 1200 sq ft shop for nearly 5 years now. I have done a writeup on it and have some poop posted here on it in my diarys. If you want to BUILD one rather than purchase one already built, let me know and I will be glad to share what I have with you. Contact me at "rjd at robotmaker dot biz"
rj