Well, essentially it's exactly like that because all of the responses -- for and against -- are based on opinion. There is definitely a correct answer but unfortunately, I don't know what that is and it probably depends on the chemical that was stored in it. Wouldn't it be nice if Myth Busters did an episode on "Smoking Myths' and settled it once and for all?
I think the majority err on the side of caution which I would say is a good thing. At least that can't hurt you. But it would be nice to know for sure.
One thing I can't understand is why people say "burn it out" then "take it to a car wash"? I'm not sure what the car wash is going to remove that the fire did not. Plus, if the car wash owner catches you, he's going to be pissed and likely call the cops.
If you were bound and determined to use it, I would build a big ^%$^% fire in it, then wire brush it down to bare metal, then build another big &^*&* fire in it then wire brush it again. Then stick your head in it and if you can still smell solvent or anything else suspicious, I'd think twice about using it. If it did not have a strange smell, I would guess -- and that's just a guess -- that it would be okay.
Hmm . . . I'm gonna have to do a little research and see if I can find a source to email this question to. Would be interesting to find out from some chemists or metalurgists (SP) or something. Trouble is, I really don't know where to start yet. But if I come up with anything, I'll report back.