Diesel engines have higher combustion efficiency, high efficiency, durability, and reliability together with their low-operating cost and emit lower carbon dioxide, carbon monoxide, and unburned hydrocarbons compared to gasoline engines; however, diesel engines are a major source of NOx and particulate matter emissions. The purpose of water-in-fuel emulsion is to enhance combustion efficiency, which improves fuel consumption rates and reduces exhaust gas emissions. Combustion efficiency is obtained by micro-explosion phenomenon, where the sub-droplet of water in the fuel spray droplet will expand and puff, breaking down the fuel spray droplet into smaller particles. The smaller the fuel spray droplet sizes are the easier the fuel will burn, improving fuel consumption rates which will reduce the reliance of hydrocarbons fuels, and reducing exhaust gas emissions, which will contribute to the reduction of greenhouse effect, without any me-chanical or electronic changes to the engine.