The aim of this study was to analyze the fuel blend combustion characteristics on an engine. First, physical properties were obtained by measuring specific gravity, API gravity, aniline point, viscosity, density, flash point, cetane number and heating value. Subsequently, combustion analysis was carried out under laboratory condition using hydra one cylinder direct injection diesel engine, while the combustion characteristics tested in this study included cylinder gas pressure, total heat release and ignition delay. The performed research showed that terpene compounds content of clove oil acted as mediator agent between the bio-additive and base fuel resulting a perfect solution. Ultimately, it enhanced the process of mixing between clove oil fuel blend and air, promoted rapid combustion and lowered ignition delay. The highest total heat release was inferred to be oxygen content of the bio-additive, leading a decrease of smoke, CO and HC emissions. However, the improvement of combustion performance did not linear with the increase of the oxygen supply as shown by eugenyl acetate. NOx emission, as an environmental consequence of an efficient process in combustion chamber, was strongly affected by the greater quantity of oxygen. (C) 2012 Elsevier Ltd. All rights reserved.