The fuel molecule cluster of the gas energy-saving device enters multiple opposite polarity RWCS strong magnetic fields, and charged particles are forced to accelerate forward and backward multiple times, causing strong oscillations. The large molecule cluster is dispersed into small molecule clusters, and arranged in an orderly manner according to the polar interval of the last magnetic field. The hydrogen atom changes from reverse hydrogen to positive hydrogen, and the activity is enhanced. Therefore, the oxygen receiving area of the fuel increases, and it combines more fully with oxygen, resulting in more complete combustion. This not only saves fuel usage, but also reduces the corresponding amount of carbon emissions and other exhaust emissions.