Fossil fuel supplies are being depleted and environmental pollution is increasing due to the transportation and industry sectors' growing intensification. Biodiesel is a cheap, abundant, and environmentally beneficial fuel source that may be used. This study aims to reduce pollution in diesel engines by adding L-ascorbic acid, an antioxidant, to palm oil biodiesel (PB20, 20% palm biodiesel + 80% diesel). Solvent extraction was used to obtain palm oil from the discarded palm. Alkali transesterification was used to turn palm oil into biodiesel. Fuel samples consisting of 90% biodiesel + 10% L-ascorbic acid (PB20L10) and 95% biodiesel + 5% L-ascorbic acid (PB20L5) are created with varying percentages of antioxidant ingredient added to the biodiesel. The results of the experimental study show that, in comparison to diesel fuel and PB20, the oxides of nitrogen emissions from PB20L5 and PB20L10 are much lower. The brake thermal efficiency (BTE) is also reduced with an antioxidant added to biodiesel in comparison with PB20. Additionally, PB20 emissions increased modestly when antioxidant ingredient was added.