also do not forget ( tongue in cheek)
to try:
Volatile organic compound - Wikipedia, the free encyclopedia
MEK , methyl ethyl ketone (really bad for lungs)
Nitro Glycerine.
and nitro Methane.
and oil based paint tinner.
Ammonia
Benzene ( more cancer causing agent)
Chloroform
Diethyl Ether
Hydrogen Cyanide
Toluene
lamp oil
xylene (cancer causing , do not try it.)
LNG
or start at link, and work down the list , one of these might be cheap and might help MPG.
but in the end , gasoline is only $1 a liter (about).
you cant beat that?. ( unless you have a subsidy )