The continuous growth in energy demands due to the ever-growing population, fast depleting fossil fuel reserves, and over-dependence on petroleum-based fuel and the corresponding economic developments have persuaded inventors to look for alternative sources of energy to avoid the future lack of diesel fuels as energy resources. Waste cooking oil (WCO) biodiesel blends are used as alternative fuels in diesel engines due to their low cost and low toxicity. In addition, they are renewable in nature and contribute the least amount of net greenhouse gases to the atmosphere compared to emissions from carbon dioxide (CO2), smoke, and nitrogen oxides (NOx). In the present paper, we discuss the results we obtained on the effects of biodiesel blends on a single cylinder diesel engine in relation to their performance and emission characteristics under varying load conditions. The experiments were performed on a Kirloskar TV-1 single cylinder 4-stroke diesel engine with a compression ratio of 17.5 and rated power of 5.2 kW at 1500 revolutions per minute. From the analysis, it was found that for the WCO 20 blend, the brake thermal efficiency and brake specific energy consumption showed slight reductions of 25.20% and 2.61%, respectively, while the exhaust gas temperature increased by 2.33% under the maximum loading condition. Moreover, considering the emission analysis, there were drastic reductions in hydrocarbon, carbon monoxide, and smoke opacity by about 58.73%, 14.26%, and 34.61%, respectively, at the expense of enhanced NOx and CO2 by 2.11% and 1.14%, respectively, for the aforementioned test fuel blends compared to diesel fuel under the highest loading condition. © 2022 by Begell House, Inc.