## 1 Introduction  
The growth of the human population and a higher quality of living have increased global energy consumption. One of the most significant consumers of energy is the transportation field [1; 2]. Transportation is heavily dependent on gasoline and diesel engines. Nevertheless, compared to gasoline, diesel engines are more cost-effective and energy-efficient [3; 4]. Diesel has also become preferable because of its higher fuel efficiency, energy density, and lower carbon dioxide (CO\({}_{2}\)) emissions [5; 6]. Thus, diesel engines provide higher mileage [7]. However, factors such as the increasing price of world crude oil, the decline in fossil fuel, and the increase in greenhouse gas emissions have forced researchers and scientists to find renewable and sustainable energy resources [8; 9; 10]. Furthermore, the health issues resulting from the exhaust of fossil fuel engines are causing alarm across the world [11; 12]. Therefore, scientists and researchers are now searching for more renewable, sustainable and cleaner alternatives to replace fossil fuels [13; 14]. Scientists and researchers are looking for ways to develop alternative fuels to deal with escalating energy demands [15; 16; 17]. In this regard, biodiesel or fatty acid methyl ester (FAME) is a potential substitute for petroleum-derived diesel in vehicles [18; 19]. Biodiesel is usually produced by transesterification of edible oil or animal fats [20; 21]. However, nowadays, biodiesel are also produced from the transesterification of non-edible oils, waste cooking oil, macroalgae, animal fats, and microalgae [22]. Thus, the sources used to produce biodiesel are sustainable and renewable [23]. Moreover, the biodiesel feedstock can be replenished by cultivating crops and rearing livestock. In contrast, the sources of fossil fuel are non-renewable [24]. Biodiesel blends have been used without making any significant modifications to diesel engines. Biodiesels are potential alternatives for diesel because of their chemical and physical properties [25; 26]. Biodiesel utilization in unmodified diesel engines slightly increases brake-specific fuel consumption and NO\({}_{\text{x}}\) emissions. However, biodiesel consumption significantly decreases CO, unburned hydrocarbon (HC), and particulate emissions due to more oxygen and the lack of aromatic content in biodiesel [27; 28]. Various research studies have been performed on engines to examine the performance and emission characteristics of _Calophyllum inophyllum_ and palm biodiesel blends [29]. A number of experimental studies have also been performed on the production of _MOB_ and its physicochemical properties. However, there are no comparative studies to date regarding engine performance and the emission characteristics of _MOB_ and its blends of 10% and 20% with diesel in an SCD. This provided the motivation and purpose of this study, which may also potentially assist in the future generation of alternative fuel. Therefore, the engine performance and emission characteristics resulting from regular fossil diesel and all _Moringa oleifera_ methyl ester blended fuels were investigated. [PERSON], [PERSON] [30] experimentally examined exhaust gas emissions from a compression ignition engine fueled with palm biodiesel. A Bosch gas analyzer was used to analyze the engine exhaust emission parameters for 250 h at a 2000 rpm engine speed. A significant reduction in CO and CO\({}_{2}\) emissions was recorded as the biodiesel concentration increased in blends. This was due to an excess amount of oxygen, which results in complete combustion occurring in the combustion chamber. [PERSON] and [PERSON] [31] examined the performance and emission characteristics of the CI engine palm oil methyl ester (biodiesel) blended with pure diesel. As a result, BSFC and brake power (BP) increased by 7.5 and 2.5%, respectively. A significant reduction of 86.89% in CO, 14.29% in HC, and 67.65% in smoke opacity were observed for palm biodiesel. However, the palm oil methyl ester enhanced NO\({}_{\text{x}}\) emissions by 22.1%.