Wide Range of Flammability
Hydrogen has a wide flammability range in comparison with
all other fuels. As a result, hydrogen can be combusted in an
internal combustion engine over a wide range of fuel-air mixtures.
A significant advantage of this is that hydrogen can
run on a lean mixture. A lean mixture is one in which the
amount of fuel is less than the theoretical, stoichiometric or
chemically ideal amount needed for combustion with a given
amount of air. This is why it is fairly easy to get an engine to
start on hydrogen.