Will adding hydrogen into the vehicles Air Intake decrease Petrol usage ?

Internal combustion engines are not very (15-45 percent) efficient. Using that engine to generate hydrogen, which then is used as fuel in the same engine is just downgrading efficiency an additional step. To boost efficiency, we'll need to do an automobile make-over. Efficient cars will be lighter and smaller, streamline. Acceleration: hydraulic pressure from tank to turbines in the wheels. Braking: primarily the result of hydraulic turbines in the wheels pressuring the tank (a reversal of the acceleration process), not friction. Cruising speed: electric motor.