{To the people not capable of working with catastrophic potentialities. Don't try this at home.}
Just looking for the same information about the oil in heaters. So I removed the heater element (exactly the same type as a small hot water tank heater element ) from a nonfunctional heater and put a small drop of the oil on a stick match, lit the match and the oil burned like any light petroleum oil. It has the viscosity of sewing machine oil or a bit less. But its flammable!
Would mineral oil or other commonly attainable oil not know for it flammability work. I may experiment (in a explosion proof environment [which I don't have yet]) and let you know.
EFC
nedwired
October 2009