An environmentally friendly and energy-secure approach is to recycle waste cooking oil (WCO) for use in diesel engines. In place of costly pre-heating and trans-esterification, diesel-WCO-alcohol ternary blends offer a simple and affordable way to use both a bio-component and a recycled component to substitute diesel and lower the viscosity of WCO partially. This investigation tested three fuel samples: 20% waste cooking oil, 65% DF, and 15% n-pentanol; diesel fuel, which served as the reference; and 5% waste cooking oil and 95% DF. The 200-hour endurance test was performed on the single-cylinder CI engine. An atomic absorption spectrophotometer equipped with hollow cathode lamps for every element was used to quantify the engine wear debris, and scanning electron microscopy and energy-dispersive X-ray spectroscopy procedures were employed to analyze the elements and measure deposit accumulations. Furthermore, temperatures at and around the injector tip caused by modern diesel injection systems may result in incredibly persistent deposits. After prolonged use, some fuels can damage the engine itself, generate excessive carbon and lacquer buildup, and make an engine operate less efficiently. The proportion of carbon layer on injector surfaces for DF, DF95WCO5, and DF65WCO20Pe15 is 32.54%, 56.17%, and 27.58%, respectively. In this experimental investigation, the fuel DF65WCO20Pe15 showed minimal injector deposit buildup.