Candlenut, a renewable biodiesel synthesized via transesterification, offers a sustainable alternative to fossil-based diesel. This study aims to produce candlenuts using a transesterification method with methanol as a catalyst. Candlenut was blended with conventional diesel in varying volumetric proportions of B20, B40, and B60 to assess its viability as an alternative fuel. Furthermore, ultrasonic dispersion was used to incorporate TiO2 nanoparticles into the biodiesel blends to enhance fuel properties, and the physicochemical characteristics of the nanoadditive-enriched fuel blends were systematically analyzed. A comprehensive experimental evaluation of combustion, performance, and emission parameters was conducted on a single-cylinder diesel engine using these modified fuel blends, with baseline diesel operation as the reference. The findings indicate that the B20 biodiesel blend, which has been added with TiO2 nanoparticles, shows superior combustion characteristics, improved performance, and emission characteristics in comparison to conventional diesel. © 2025 Elsevier B.V., All rights reserved.