Processes such as fast pyrolysis of whole biomass or base-catalyzed depolymerization of lignin produce complex mixtures Of oxygenated compounds that must be upgraded to be suitable for blending with petroleum and processing in a refinery. Complete removal of these oxygenated Compounds is exceedingly energy intensive, and it is likely that upgraded pyrolysis oils will contain up to 2% oxygen content to be economically viable. The purpose of this study was to evaluate the effect of the presence of oxygenated chemical components representative of those present in upgraded pyrolysis oil on diesel engine performance and emissions. Engine testing was performed by blending seven different oxygenated components and one multicomponent blend with certification ultralow sulfur diesel fuel and quantifying the performance and emissions from the combustion of these fuels in a four-cylinder, turbocharged, 4.5 L John Deere PowerTech Plus common rail, direct injection diesel engine that meets Tier 3 off-highway emissions specifications. The properties of the oxygenated fuel components were fully characterized in accordance with ASTM diesel fuel standards. Gaseous emissions measurements included CO, CO2, NO, NO2, and total hydrocarbons; particulate measurements were performed on a PM10 basis. The residual oxygenate blends exhibited very few statistically significant differences compared to diesel at lower blend levels (2 vol %) but negative effects were observed at higher blend levels (5-6 vol %).