A stationary diesel engine is tested using HHO produced on board by a commercial electrolytic cell as additive. The cell uses KOH as electrolytic and is connected to the engine battery. Experiments show the cell efficiency is better when current is 6-10 A. Engine was tested in several load regimes, measuring fuel consumption and others parameters, including vibration. Results shows that BSFC and thermal efficiency with HHO improves an average of 3,81% and 2,79% respectively, depending on engine regime and load. Vibration is evaluated using RMS and peak-to-peak values of vibration acceleration, measured in two points on top and one side of the engine. The addition of HHO reduces vibration in most of the experimental points, ought to a better combustion process of gasoil in presence of hydrogen. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.