A big part of the smell is also the additives in motor gas. Not much of a need for addtives in Coleman fule, and avgas as minimal additves in it since it is refined so specifically. Also, avgas has a higher vapor pressure than motor fuel, eliminating some of the nasty smelling parts of gasoline needed to run. Avgas also evaporates much faster (lots of Toluene in it!), so minimal smell.

Mark