One of the primary aims of this experimental investigation is to examine hydroxy-gas enrichment effects on environmentally friendly but performance-reducing alternative fuels such as ethanol and biodiesel. Hydroxy gas is a product of the pure water electrolysis method. Entire HHO system has integrated into engine test rig for this purpose. Two different biodiesohol fuel blend prepared and named by their volumetric compositions. Biodiesohol used to describe biodiesel, ethanol and standard diesel blends. Specific fuel properties are measured and ensured to be in EN590 and EN14214 standards. Experiments were conducted on a single cylinder diesel engine which was fuelled with diesel-biodiesel-ethanol fuel blends those enriched by 1 L per minute HHO gas during the entire tests. All of the experiments performed under full load condition within the range of 1200-3200 rpm engine speed. From the view of performance; brake power, brake specific fuel consumption and thermal efficiency results discussed. Besides, carbon monoxide and nitrogen oxides results measured and presented as exhaust emission. Standard diesel fuel outputs determined as a reference line to analyze the changes. A number of studies have been conducted with fuels used in this experimental study and their mixture in different ratios as well, but an examination of the HHO addition to biodiesel is performed for the first time in this research area of the literature. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.