Abstarct: Abstract In recent decades, there has been a sharp increase in demand for electricity and clean fuel. As a new energy carrier, hydrogen can be converted to other forms of energy with higher efficiency and very clean combustion compared to other fuels. In this research, hydroxy gas (HHO) is produced as an agent to improve fuel and reduce engine pollution by the electrolysis of water and is transferred to the vehicle's combustion chamber as a supplement. In the initial tests, the effective parameters including the distance and number of electrode plates, the wiring of the plates, the height of water and the concentration of potassium hydroxide electrolyte (KOH) are investigated. Then, in three steps, using the design of experiments of Box-Behnken and Taguchi experiments, the optimal values were generated and analyzed to produce the highest cell efficiency. The results of optimization of test design baxsed on hydroxy gas production efficiency (LPH) and production rate in terms of energy consumption (LPH / Watt) show that the highest cell efficiency at the highest immersion height in water (20 cm), the highest electrolyte concentration (2 gr/Lit) and the smallest distance between the plates (3 mm) is produced. Also, due to the effectiveness of using an ultrasonic transducer in increasing cell efficiency in the Taguchi method, an ultrasonic transducer with an amplitude of at least 40% and a percentage of time-On of at least 10% is used in the cell. The use of optimally designed and built-in cells in the national car engine, in the case of gasoline fuel, shows a 16% reduction in hydrocarbon (HC) and an 87% reduction in CO emissions and a reduction in fuel consumption of 3.4 % in slow-cycle operation is predicted. In natural gas fuel mode, HC gas 18%; CO gas 33% and CO2 gas 0.9% is decreased. Due to the high pollution of HC gas and the production of large amounts of this gas in CNG engines; The production and injection of hydroxy gas can be a solution to reduce unburned hydrocarbons and reduce the release of this gas into the environment.