Combustion of water-containing diesel fuels results in a simultaneous reduction of soot and NOx-emissions, i.e. they partially avoid the so-called soot-NOx trade-off. In the frame of the present work new temperature invariant, highly efficient fuel microemulsions of the type water/antifreeze – diesel fuel - oleic acid/monoethanolamine/oleic acid diethanolamide containing up to 24 wt.% water with appropriate physical characteristics for commercial applications were formulated. As unexpected reward of the investigations on formulation of microemulsion fuels, novel water-in-fuel nanoemulsions (< 200 nm) were obtained featuring substantial reduction of surfactant content, an interesting economical aspect. Exhaust gas emissions, soot-structure and size distribution of water containing fuels compared to pure diesel fuel were analysed. The results show that using load-dependent water containing fuels yield a drastic reduction of soot up to 98 % (FSN) as well as nitrogen oxide emissions up to 62 %.