Probably because these two paragraphs, upon which the justification to use
acetone rely on, were written by someone who has little understanding of
chemistry.

Water will reach 300 °F before vaporization under pressure.  However, is the
gasoline under pressure once it's been released by the fuel injector?  No.
In addition, the surface tension of gasoline is remarkably low compared to
water.  Just try floating a sewing pin on gasoline.  Now try it again with a
second clean pin on water.  Gasoline is mostly a non-polar fluid, thus it
has extraordinarily few hydrogen bonds in it compared to water which are
responsible for creating water's surface tension.  Moreover, water will
vaporize quite nicely even at room temperature.  Just put a mL of water in
an open dish on a sensitive balance, one measuring in grams to at least 4 or
5 decimal places.  The balance will never equilibrate due to the continuous
loss of water to the vapor phase.  For each mg lost, a µL of water has been
lost to the vapor state right before our eyes.  Now for comparison, put the
water in a small enclosed container.  The container will "lose" weight for a
short period of time but then quickly stop as the air in the container
becomes saturated and the number of water molecules leaving the bulk water
for the vapor phase reaches equilibrium with the number of water molecules
in the vapor phase returning to the bulk liquid water.  For fun, repeat the
experiment with gasoline.  What you'll find it that the gasoline "loses"
weight more quickly.  That's due to it's higher vapor pressure.  A higher
vapor pressure means that it's easier for gasoline molecules to enter the
vapor phase.  Why?  There's far fewer polar bonds thus there's much less
hydrogen bonding holding the gasoline molecules in the liquid phase.  The
hydrocarbon molecules in gasoline are held in the liquid phase primarily by
london forces due to the instantaneous polarizability of the electron
clouds.  London forces are considerably weaker than the hydrogen bonds found
in polar molecules.  Thus, we've just demonstrated that gasoline will
vaporize much more easily than water and is indeed quite dissimilar with
respect to surface tension contrary to the claims made in the article.  Now,
if someone with a sensitive balance has some time on their hands, then it
would be fun to test the article's hypothesis that a small amount of acetone
will noticeably raise the vapor pressure of gasoline.  Any volunteers?  

Natural frequency?  Inherent molecular vibration?  Every molecular bond will
have stretching and bending frequencies which are unique to a particular
type of bond, including the molecular bonds found in both gasoline as well
as acetone.  Lower the temperature and these will decrease.  At 0 °K they're
all gone!  Maybe they would suggest preheating the gasoline?  That would
certainly increase it's "inherent molecular vibration".  I'm curious how
they determined that the bonds are "sluggish".  Wishful thinking perhaps?

The author isn't very good at math either!  For example, 1 part in 3000 is
0.033% while 1 part in 5000 is 0.02%.  Moreover, 3 oz. per 10 gallons is
0.23%.

Overall, the article is entertaining to read but probably not useful for
much else.

Eric