The co-combustion of fuel has substantial advantages when compared to normal combustion and it requires very little modification. In this perspective, ethanol supplement co-combustion with biodiesel is proposed. The co-combustion characteristics were studied by manifold induction of vaporized ethanol and direct injection of waste cooking oil biodiesel. A vaporizer system was fabricated to produce vaporized ethanol in a volumetric basis (10% and 20%, respectively). It was revealed from the experiments that with co-combustion of oxygenated biofuels, the combustion advanced and peak pressure shifted to TDC. The pressure rise rate decreased with the increase of vaporized ethanol induction and the maximum rate of pressure rise reduction was noted with biodiesel-20% ethanol induction which was 4% lower than biodiesel-10% vaporized ethanol induction. On the other hand, the maximum rate of heat release rate (60.24 J/degrees CA) was seen in biodiesel with 20% ethanol induction. Furthermore, the co-combustion studies disclosed a two-stage heat release pattern (low temperature and high temperature reactions). It was observed that the increase in ethanol concentration extended low temperature region by 1 degrees crank angle and retarded high temperature region by 3 degrees crank angle.