© 2021 Taylor & Francis Group, LLC.In this study, diesel fuel was enriched with hydrogen and boron, which are used as environmentally friendly energy sources in recent years. A special fuel additive (octamix) was obtained by mixing ethanol, ammonia boron and trioctyl borate and the effects of octamix-diesel fuel blends on diesel engine responses were analyzed at different engine loads (from 500 W to 3000 W) and a constant engine speed (3000 rpm). Test fuels were prepared by adding 0.5% (0.5 OCT-D), 1% (1 OCT-D), 2% (2 OCT-D) and 3% (3 OCT-D) octamix into the diesel (100D) by volume. Brake thermal efficiency (BTE) increased while brake specific fuel consumption (BSFC) decreased with increasing octamix up to 1% percentage. With 1 OCT-D fuel, the maximum BTE was achieved as 26.2% at 3000 W load, while the minimum BSFC was 180 g/kWh at 2500 W load. An increase of 3.19% and a decrease of 18.18% were achieved, respectively, compared to the 100D. On the other hand, nitrogen oxide (NOx), carbon monoxide (CO), carbon dioxide (CO2), hydrocarbon (HC), and smoke emissions have been reduced by up to 1% octamix percentage. Compared to the 100D, a decrease of 15.66%, 46.67%, 23.63%, 24.24%, and 10.71% was achieved, respectively.