In recent experiments with two wood-derived flash pyrolysis oils manufactured through the NREL and ENSYN processes, it was found that the NREL oil exhibited considerably better ignition characteristics than the ENSYN oil. An investigation was conducted to explore the relationship between pyrolysis production parameters and combustion characteristics, and to explain the observed differences between the ENSYN and NREL oils, This will help guide pyrolysis oil production. It was found that the most important parameters were water content and the severity of thermal cracking, with lower water content and greater cracking yielding better performing oils. The differences in volatiles collection and in physical properties were found to be less important.