Abstract: Ferrofluid -diesel blend are fuels for regular diesel engines. The advantages of ferrofluid diesel blend are reductions in the emissions of nitrogen oxides and particulate matters, which are both health hazardous, and reduction in fuel consumption due to better burning efficiency. An important aspect is that ferrodiesel can be used without engine modifications. This paper presents the influence of ferrofluid on the emissions and on the combustion efficiency. Whereas there is a decrease in emissions of nitrogen oxides and particulate matters, there is an increase in the emissions of hydrocarbons and carbon monoxide with increasing ferrofluid content of the blend. The combustion efficiency is slightly improved when ferrofluid is blended with diesel