<p>Biodiesel, due to its oxygenated structure and higher cetane number compared to petroleum diesel fuel, enhances combustion profiles within engine chambers. However, it poses challenges, such as elevated NOx emissions which are attributed to its higher flash point. To mitigate this issue, researchers have investigated the incorporation of nanoparticles into diesel–biodiesel blends. In this study, we synthesized CaO-Al₂O₃ mixed structure- a catalyst frequently utilized in biodiesel production- as a fuel additive which synthesized via simple and cost-effective solution combustion method. The synthesized CaO-Al₂O₃ mixed structure exhibited a calcium aluminate (CaAl) framework with nanosized particles, a high surface area, and a significant oxygen storage capacity (OSC) of 2740&#xa0;µmol/g. The incorporation of CaAl nanoparticles demonstrated numerous advantages, including enhanced engine performance (1–5% increase in power, 5–20% improvement in BTE, 1–10% reduction in BSFC, and 2–30% decrease in EGT). Moreover, the nanoparticles improved combustion efficiency by accelerating complete combustion, evidenced by a 4–19% increase in CO₂ emissions and a reduction of CO and HC emissions. CaAl's capacity to alter its structure and release oxygen during combustion reactions contributes to these improvements. Furthermore, a notable reduction in NOx emissions, over 12%, was observed. This can be ascribed to the high specific heat capacity of CaAl, which absorbs the heat released during combustion reactions, thereby preventing a rise in chamber temperature and limiting the reaction between nitrogen and oxygen. These findings highlight the potential of CaAl as a valuable fuel additive, broadening its application beyond its traditional role as a catalyst in transesterification reaction.</p> Graphical Abstract <p></p>