A mixture of ethyl acetate (EtAc), ethyl propionate (EtPr), and ethyl butyrate (EtBu) can be obtained from low-value biomass wastes in a simple biochemical process that includes acidogenic fermentation. Their proportions in the mixture vary according to fermentation conditions and biomass feedstocks. To help direct the fermentation process, they have been previously analyzed separately in a homogeneous charge compression ignition (HCCI) engine, but the characteristics of the mixtures are unknown. Using mixture design, we investigated how the tricomponent fuel blends of these esters impact the combustion characteristics in HCCI. This paper reports the ignition timing for 12 different blends. It characterizes the direct effect and the types of interaction using a blending model. The ignition timing is mainly determined by the proportion of EtAc and EtBu, with EtBu having a smaller ignition delay than EtAc. EtPr has no appreciable direct effect on this timing, but it has an antagonistic effect on EtAc and EtBu. The faster ignition of EtBu could help decrease the inlet temperature and, therefore, be more compatible with real engines. Moreover, dilution with EtPr could also reduce the effect of mixture variability. The successful implementation of these esters in HCCI may, however, require blending them with other fuels to further decrease the inlet temperature. This will remain the focus of future studies. © 2011 American Chemical Society.