Good example of learning the hard way, thankfully for him not as hard as it could have been. The notion of "oil not working that way" is kinda silly. It's still a hydrocarbon, the same stuff gasoline and diesel fuel is, just a heavier molecular weight. Given the right conditions, enough heat to vaporize it, and you've got a combustible.

Just an aside, if you want a 55 gal burn barrel/garbage can, try to find a grease drum, they have a removable top held on by a band clamp. No cutting required (though perhaps some messy cleanup depending on how clean you need it )