Recycling oil from scrap rubber products, especially scrap tires, has contributed to reducing the use of fossil fuels. However, the impurities in recycled oil and the large emission of pollutants from the oil are problems yet to be solved. Therefore, the efficient use of pyrolysis oil (PO) from scrap tires needs investigation. We investigated the combustion efficiency, pollutant emission, and physicochemical properties of three different types of diesel (PO, 0# diesel CNPC, B100) and two mixtures (PO with 0# diesel CNPC and PO with B100) by testing and measurement. The mixtures had better properties, higher efficiency, and lower emission of pollutants (CO, HC, NOx, particulate matter) from an engine than each type of diesel. Similar output power was obtained for both tested fuel mixtures in this study. To obtain similar performances to 0# diesel CNPC and PO with B100, it was necessary to adjust the engine control module (ECM). The results of this study provide information on how to use recycled fuels effectively with refined diesel, which suggests a way to reduce the use of fossil fuels and the emission of pollutants.