Taken from air engine:
"We have never claimed that the thermodynamic graphs of our engines would be adiabatic (nor are they isothermic). Mileage presents no problem - the volume and pressure of air in the car can be increased considerably. (by changing the tank size or the air pressure). The data published at this link, should help to re-establish the truth and give definitive information on these two points."
first law of thermodynamics says:
Energy can neither be created or destroyed, heat and mechanical energy are mutually convertible.
second law: entropy tends to rise over time.
It seems they are just storing energy for other uses.but since you can not create energy ,the best you can do is make a more efficient engine.
I don't have time right now to review entire engine right now but ,it may be more efficient,but not by 75% fuel consumption in my opinion just to take a wild guess, I will always take a good look at new technology ,but it has to follow thermodynamic laws. no exceptions.
The Laws of Thermodynamics say:
Zeroth Law: "You must play the game."
First Law: "You can't win."
Second Law: "You can't break even."
Third Law: "You can't quit the game."
Do you wanna Play Thermodynamics ???????? I forgot "you must"