I don't 'claim'.. I'm 'doing' it
48% fuel efficiency in a Toyota Truck '95 ...... right now!!
Note that the results are not simply caused by the displacement of a small amount of fossil fuel with an equivalent volume of hydrogen. Rather, the increase in efficiency is gained by getting more useful work out of the fossil fuel itself, resulting in less energy wasted in the form of heat.
Electrolysis, itself, is well understood and it has been known for over thirty years that the addition of hydrogen to fossil fuels, burned in internal combustion engines, will increase the efficiency of that engine. This premise has been validated by a number of papers published by the Society of Automotive Engineers (SAE). The concept is valid with any fossil fuel (diesel, gasoline, propane, natural gas) or bio-fuel (biodiesel, ethanol) though it is most effective in diesel engines. Among other, more subtle effects , the presence of the hydrogen alters the initial stages of the unfolding combustion dynamic, altering the kinetic chemical pathway which the combustion follows. The net effect is to alter the time at which maximum heat energy is released relative to the power cycle, increasing the adiabatic efficiency of the engine (typically a modern diesel engine runs around 40% efficient - an increase of only 4% in the adiabatic efficiency results in a 10% decrease in fuel consumption!).