This work reports on an extensive investigation of the physicochemical properties, engine performance, exhaust emissions, and fundamental energy and exergy parameters of waste‐plastic oils blended with an additive, diethyl ether and diesel. A four‐stroke single‐cylinder diesel engine was used for the engine experiments. The seven fuels in this study include a neat diesel, a neat waste plastic oil, two binary blends of diesel‐waste plastic oil, and three ternary blends of diesel with waste plastic oil and diethyl ether. The justification for selecting diethyl ether was to augment fuel properties in the blend and to further reduce emissions. The reasons for choosing waste plastic are not only to harness energy from waste plastic but also to offer an effective solution to the plastic waste management issue. The choice of diesel was to use it as a reference fuel for comparison with other fuels. Fuel properties were observed to be similar, and in some cases better, with the blends. Notable reductions in emissions with identical engine performance and energy and exergy parameters were observed with the five oxygenated blends (plastic oil blends) than with a reference diesel fuel. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd