Five fuels were tested in a common rail direct injection (CRDI) diesel engine to see how they affected soot particle distribution and the engine's controlled and unregulated emission characteristics (M15, M25, and M35). The findings demonstrated that regulated emissions of carbon monoxide (CO), hydrocarbons (HC), and particulate matter (PM) could be efficiently controlled to a very low level when mahua oil biodiesel (MOB) in diesel was utilized in conjunction with ideal engine working situations. Paper filters were employed to remove diesel dust. Entire particulate matter main particles were < 100 nm in width, with the average diameter for the biodiesel mixes falling among 20 and 26 nm. PM particles had uncontrolled emissions including Pb, Mn, and Ba, while M100 had 56.72% fewer xylene emissions, 22.49% fewer toluene emissions, and 19.45% fewer benzene emissions compared to M0. As a result, MOB is a wonderful option for reducing pollution from diesel engines and other sources, both in the form of controlled and unregulated emissions. © 2024 Elsevier B.V., All rights reserved.