An additive has been prepared for blending with gasoline that facilitates a cylinder resident reaction, in high compression internal combustion engines (ICEs), to produce an increase in engine's mechanical energy output. A method of increasing mechanical efficiency of an internal combustion engine (ICE) comprising blending an amount of additive with gasoline to perform hydrolysis of olefin hydrocarbons, represented by octene (C8) into petroleum gas hydrocarbons, represented by butane (C4), wherein the additive facilitates cylinder-resident reaction, aided by a low concentration of organometallic catalyst, to utilize the elements of the water combustion product, to hydrolyze olefin hydrocarbons such as octene, resident in the gasoline, into petroleum gas hydrocarbons such as butane, and to increase the ICE's efficiency of utilization of the energy of the fuel.