I have a 100,000 BTU one built by Eliminator. Works very well, but you have light it off to get it started the first time. You also have to clean it frequently, but you will have to do that for any waste oil only burner. They build soot like crazy
To get the hands off performance, you need one with a gas assist.
I burn about 8-12 gals every 24 hrs with the furnace at idle. Full on, it will suck 20 gal down in about 8-10 hours. Mine almost never comes off idle in my garage.