An experimental study is conducted to evaluate the effects of using diesel fuel blend with diethyl ether (DEE) 24% by vol., a promising fuel that can be produced from biomass (bio-DEE), on the combustion behavior of a standard, direct injection, 'Hydra' diesel engine. Combustion chamber and fuel injection pressure diagrams are obtained at four loads, using a high-speed, data acquisition and processing system. A heat release analysis of the experimentally obtained cylinder pressure diagrams and plots of histories in the combustion chamber of the gross heat release rate (HRR) and other related parameters, reveal some interesting features of the combustion mechanism when using DEE blend. Cylinder pressures and temperatures are reduced, HRR diagrams are delayed, and the engine runs overall a little 'leaner' at reduced heat losses, with the DEE blend compared to neat diesel fuel for all loads. Moreover, given the shown low ignition quality of DEE/diesel fuel blend and reports for unstable engine operation at high DEE blending ratios, the strength of cyclic (combustion variation) irregularity is examined as reflected in the pressure indicator diagrams, by analyzing for the maximum pressure and rate as well as dynamic injection timing and ignition delay, using stochastic analysis for averages, coefficients of variation, probability density functions, auto-correlations, and cross-correlation coefficients. The stochastic analysis reveals the randomness of fluctuation phenomena observed in the engine, and the cross-correlation coefficients showed that neither the injection process nor the DEE/diesel fuel blend had practical effect on cyclic irregularity. (C) 2013 Elsevier Ltd. All rights reserved.