Biodiesel represents one of the alternate fuels that can be used in combustion engines due to its provenance that it has the ability to reduce emissions. Biodiesel is an eco-friendly, naturally occurring, renewable, and perishable fuel. Using biodiesel reduces the demand for imported fossil fuels, whose supply is rapidly depleting and whose price is being tested. An experiment assessed a diesel engine’s combustion, emission, and performance with lemon grass methyl ester and its blends (20 percent diesel & 15 percent Di-Ethylene Glycol (DEG)). Biodiesel can find use in Low Heat Rejection (LHR) engines in a highly efficient and effective manner when the combustion chamber temperature is maintained by a thermal layer in the surface piston crown. In the current work, approximately 0.5 mm of ceramic material (La2Ce2O7) was plasma-sprayed onto the piston crown. The tests were directed in a Direct Injection (DI) diesel engine utilizing two different combinations of Lemongrass oil Methyl Ester (LGME) according to varying loads along with and without an adiabatic (Coated) piston. The findings indicate that B20 biodiesel with coating and additives increases Brake Thermal Efficiency (BTE) and reduces Brake-Specific Fuel Consumption (BSFC) by approximately 10 percent at 100% load. The LHR engine produced 20 percent more Nitrogen Oxide (NO) emissions than an uncoated diesel engine while at the same time lowering Carbon Monoxide (CO) and Hydrocarbons (HC). Both the pressure at its highest and the amount of heat release appeared substantially higher in the LHR engine than in a regular engine. © 2023 Elsevier B.V., All rights reserved.