Increased usage of plastic and absence of an efficient system to address its non-degradability has become a serious issue threatening the human life. On the other hand, increased fossil fuel consumption which led to their depletion necessitates the search for an alternative that could replace the conventional fuels and alongside abate the emissions. Both the non-degradability of plastic and need for an alternative fuel can be addressed by converting the waste plastic to useful energy. The present article reviews about pyrolysis, a chemical treatment to convert waste plastic to energy. It also focuses on its functional feasibility as a fuel in a compression ignition engine. Reportedly, waste plastic oil when used in a diesel engine yields lesser thermal efficiency, higher brake specific fuel consumption, increased emissions of carbon monoxides, and oxides of nitrogen and unburnt hydrocarbons. Irrespective of its disadvantages, it is worthwhile to note that it is waste plastic which is converted to useful energy. However, not much work on the technical feasibility and functional efficacy of waste plastic oil as a fuel in a diesel engine is reported, and hence, research in this application seems to gain its focus in near future.