Snuggles
When thinking of oil fumes from a chemical standpoint it is a valid question, really. "Oil" is a mix of several hydrocarbons, each with its own ignition point. Oil can evapourate, thus "oil vapour" (or, mostly "fuel vapour" in aviation world) and it can burn, thus "oil smoke" but it is hard to define "oil fume" chemically.
That, is a load of old men making shoes.
The word 'fume' was derived from the French
fumer and the Latin
fumare meaning 'smoke' or 'steam'. And if you did not know that, then how have you been decoding TAFs and METARs all these years? Ah, you probably weren't....
So a fume is basically visible particulates in the air. And if you have ever seen a 146 APU have a fume event, you would know that 'fume' is the correct appellation. A 146 with an overheating APU is a bit like doing evacuation drills with a smoke generator.
However - I always thought that the 146's blue cabin smoke was coming form the overheating packs, not the APU itself. The fume events only happened in the morning when the pack went banzai and could not control its temperature, and had nothing to do with the APU itself. The engines could have the same effect, if you had not warmed everything up with the APU.
And talking of fume events and ill health - what sort of oil were they putting in those smoke generators, when we did smoke training?