To provide a technology for the improvement of fuel consumption by use of a gasoline additive composed mainly of functional water.

A gasoline additive is produced by a first step of producing a powder mixture of ore and the like in which ore and the like 0101 are mixed as a powder thereof 0102 in a predetermined mixing ratio to form a powder mixture 0103 of ore and the like, a second step of filling the powder mixture of ore and the like in which the powder mixture of ore and the like is filled into a container 0105, a third step of producing functional water in which water 0104 is retained for a predetermined period of time in a water tank 0106 disposed close to the container, and finally, the final step of producing a gasoline additive in which functional water 0107 produced by taking out from the water tank after a lapse of the predetermined period of time is mixed with trehalose and the like 0108 in a predetermined ratio.