This document presents an experimental investigation into improving the efficiency of an internal combustion engine by using hydroxyl (HHO) gas as a secondary fuel. HHO gas is produced through the electrolysis of water and is then injected into the engine's inlet manifold. The researchers found that using HHO gas reduced fuel consumption by 10-30%, increased engine torque, and significantly reduced harmful exhaust emissions like NOx, CO and HC. Their results indicate that HHO gas combustion properties favor fast burning conditions suitable for high-speed engines. The document also reviews related literature and describes the experimental setup and methodology and presents results showing increased engine speed and reduced emissions with the addition of HHO gas.