Microemulsion technology was found to be a promising fuel-upgrading process for glycerol. Biosurfactant rhamnolipid (RL) was successfully tested to obtain nano-scaled glycerol-in-diesel microemulsion (GDM) and glycerol/water-in-diesel microemulsion (G/WDM). These microemulsion fuels were stored at 4 degrees C without phase separation for over six months. Fuel properties like high heating value (HHV), dynamic viscosity, corrosivity, and thermal decomposition characteristics of GDM and G/WDM were comparable to those of diesel. Thus, the microemulsion fuel may be qualified as commodity fuel like diesel. In addition, the cold flow properties cloud point and pour point of GDM and G/WDM were improved by the addition of glycerol or glycerol/water mixtures. Glycerol-the commonly used raw material for fuel additive production-could be directly introduced into fuel as cold flow property improver by microemulsion technology. (C) 2015 Elsevier Ltd. All rights reserved.