This study experimentally evaluated the performance, emissions, energy, exergy, environmental, and enviroeconomic characteristics of a single-cylinder diesel engine fueled with diesel–dimethyl ether (DME) blends and port-injected acetylene and hydrogen. Experiments were conducted at 1800 rpm under loads of 3.2, 6.4, 7.9, and 12.8 Nm. Diesel was used as the reference fuel, while DME was blended with diesel at 10%, 20%, and 30% by volume. Acetylene and hydrogen were supplied individually or together at 5 and 10 L/h. Results showed that DME addition reduced fuel energy input by 12–28% and exergy destruction by 35–68%. Exergy efficiency increased from 13 to 14% for diesel to 26% with D70DME30 and to 28–30% in gas-assisted modes. Soot, CO, and HC emissions decreased significantly, while NOx increased moderately by 8–18%. Annual CO2 emissions and enviroeconomic impacts were reduced by up to 60%, demonstrating a viable transition strategy for cleaner and more efficient existing diesel engines.