This seems like a really good heater. Also runs on diesel.
Review part 1: https://www.youtube.com/watch?v=LyiDXMZMYfc
Review part 2: https://www.youtube.com/watch?v=Ks4ecEMYWsg
Then he tries it on an inverter just to be sure that works properly: https://www.youtube.com/watch?v=cw6xJQOxSHE
This seems like the ultimate garage heater, aside from something more permanently installed (or a waste oil furnace).
It's pretty clean even on diesel which is kind of impressive. He also tests the CO2 and CO emissions in an enclosed garage with good results.