The ever-increasing fossil fuel usage and cost, environmental concern has forced the world to look for alternative biofuel in compression ignition engine. In this research work, a 60 hours endurance test has been carried out on horizontal type single cylinder diesel engine. During endurance test; three fuel samples such as D100 (%diesel fuel as a baseline), B25 (waste cooking oil biodiesel 25% and 75% diesel fuel) and B25+LPG (liqudified petroleum gas and waste cooking oil biodiesel) respectively. At the end endurance test for each fuel samples, carbon deposit was analyzed on the fuel injector while using SEM and EDX techniques. However, an endurance test was carried out at constant rpm and constant load condition. From results, it was found that the injector tip showed higher deposition of carbon in case of B25 fuel followed by B25+LPG and DF respectively.