The high viscosity of pure plant oils (POs) reduces the feasibility of using plant oils as diesel engine fuel as reported by various researchers. Fuel blending is one of the methods of lowering viscosity. A study was carried out on fuel properties of Jatropha (JO) and Croton (CROT) seed oils blended with a by-product of Songosongo natural gas extraction - natural gas condensate (NGC) (modifier) of between 5% and 50% (v/v) at room temperature (30 ± 3˚C). Mixture design was used to analyse the effect of NGC composition in the resulting blend on the kinematic viscosity and fuel combustion properties of the blends. The results were also compared to the properties of crude POs and diesel fuel (grade 4-D) specifications. The blends were found to be compatible over a wide range of compositions and exhibited much lower viscosity and better combustion properties than crude plant oil (PO) samples. The optimum parameters for formulating blends were found to depend on the modifier characteristics and that 10% (v/v) NGC was enough to produce the desired liquid biofuel blend. The characteristics of blends presented in this work meet the specifications for diesel fuel grade 4-D and so matches well with the characteristics of fuels for low- and medium-speed diesel engines. This implies that the PO/NGC blends may be potential alternative fuels in low- and medium speed diesel engines, which are common engines found in rural areas and so PO/NGC blends fuels may contribute in meeting rural’s energy self-sufficiency while at the same time making utilisation of natural gas condensate.Policy Innovation Systems for Clean Energy Security (PISCES) Research project