Disposal of waste tires is one of the most important problems that should be solved. This problem can be solved by considering waste tires for production of hydrogen or fuel for diesel engines. This paper presents the studies on the performance and emission characteristics of a four stroke, four cylinders, naturally aspirated, direct-injected diesel engine running with various blends of waste tire pyrolysis oil (WTPO) with diesel fuel. Fuel properties, engine performance, and exhaust emissions of WTPO and its blends were analyzed and compared with those of petroleum diesel fuel. The experimental results showed that WTPO diesel blends indicated similar performance with diesel fuel in terms of torque and power output of the test engine. It was found that the blends of pyrolysis oil of waste tire WTP010 can efficiently be used in diesel engines without any engine modifications. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.