The vast stores of biomass available worldwide have the potential to displace significant amounts of petroleum fuels. Fast pyrolysis of biomass is one of several possible paths by which we can convert biomass to higher value products. Pyrolysis oil (PO) derived from wood has been regarded as an alternative fuel to be used in diesel engines. However, the use of PO in a diesel engine requires engine modifications due to the low energy density, high acidity, high viscosity, high water content, and low cetane number of PO. The easiest way to adopt PO without engine modifications is blending with other fuels that have a high cetane number. However, PO has poor miscibility with light petroleum fuel oils; the most suitable candidate fuels for direct fuel mixing are alcohol fuels. Early mixing with alcohol fuels has the added benefit of significantly improving the storage and handling properties of the PO.In this study, the properties of PO were upgraded by blending n-butanol and two cetane enhancements as additives. Blending with n-butanol effectively reduced the viscosity of PO to the proper level for use in conventional diesel engines while suppressing PO polymerization, which would otherwise spontaneously produce gummy polymers. The auto-ignitability of the PO-butanol blended fuel was improved by the addition of the cetane enhancements, polyethylene glycol 400 (PEG 400) and 2-ethylhexyl nitrate (2-EHN). Experimental results showed that stable combustion characteristics were obtained for PO-blended fuels with a maximum PO content of 15 wt%. The combustion of PO-butanol blended fuels produced comparable or less hydrocarbon (HC) and carbon monoxide (CO) emissions than diesel fuel combustion over most of the engine load range. And nitrogen oxides (NOx) emissions for the blended fuel were higher than those of diesel fuel over the entire engine load range of IMEP 0.2-0.8 MPa.