The purpose of this research was to create very polydisperse concentrated heavy oil-in-water emulsions by optimizing the co-solvents, surfactants, alkali, and electrolytes in the chemical formulation, with respect to the droplet size distribution. Novel co-solvents that have shown superior performance in chemical formulations used for enhanced oil recovery have been tested. Droplet size distributions that resulted in a lower emulsion viscosity were determined, to have a higher mean droplet diameter (d(32)) and a bimodal droplet size distribution with a diameter ratio (d(32L)/d(32,s)) of > 6 and a volume fraction (phi(s)/ (phi(L) + phi(S))) of 0.2-0.3, where phi is the volume fraction of the dispersed phase and the subscripts L and S correspond to the larger and smaller peaks in the bimodal distribution. We report the effects of various chemical formulations on the droplet size distribution of heavy oil-in-water emulsions with a particular emphasis on d(32) and, for the first time, the maximum packing fraction (phi(m)) of oil droplets. A novel one-step preparation procedure is proposed to prepare concentrated multimodal oil-in-water emulsions with a new chemical formulation approach. We were able to formulate stable oil-in-water emulsions with phi(m) values as high as 0.95, which is similar to 0.30 higher than the theoretical phi(m) value for random close packed monodisperse spheres (0.64). We observed the optimal particle size distribution of concentrated heavy Oil-in-Water emulsions prepared with co-solvents for maximum packing at similar to 75% of the Na+ concentration necessary to reach the oil-in-water to water-in-oil inversion point for anionic surfactants. An important application of this study is the transport of heavy oils in pipelines.