<p>The objective of the investigation was to explore the combustion performance and pollutants emitted from a lightweight diesel engine utilizing biodiesel-methanol hybrid fuels, at a simulated altitude of 2400 m, without any modifications. The outcomes showed that the addition of methanol improved the performance and reduced emissions. In comparison to biodiesel, the blends exhibited a prolonged ignition delay and a decreased combustion duration. At lower load condition, the blends demonstrated a reduced peak in-cylinder pressure and a higher peak heat release rate than biodiesel. However, upon increasing the methanol content and engine load, the peak cylinder pressure of the blends surged, surpassing that of biodiesel. Notably, the blends achieved superior engine power compared to biodiesel at higher loads. Additionally, biodiesel consistently demonstrated lower fuel consumption across all engine loads. Furthermore, the blends exhibited a lower exhaust gas temperature compared to biodiesel. The influence of methanol mixing on NOx emissions varied significantly, exhibiting opposing trends between low and medium-to-high loads. Remarkably, an increase in the methanol ratio in the blends caused a marked decrease in soot levels, particularly at higher loads.</p>