Experimental insights into CI engine behaviour with ternary diesel blends of treated waste oil and high-chain alcohols

• Ternary diesel–waste oil–higher alcohol blends were experimentally evaluated. • Octanol and butanol affected combustion stability and in-cylinder behavior. • DWO20 achieved higher thermal efficiency at low–medium engine loads. • DWB20 emitted more CO 2 due to the carbon-rich treated waste oil. • Alcohol blends lowered NO X via latent heat effects, except at 50% load. The transition from conventional fossil-based fuels to renewable alternatives holds great promise in advancing more sustainable transportation. This present experimental study investigates the effects of high-chain alcohol-based fuels, octanol and butanol, under conditions of treated waste engine oil and diesel fuels in a compression ignition (CI) engine on combustion, performance and emission parameters. Three fuel blends were examined at varying pedal positions (20–50%), with a 10% increment. The tested fuel blends were a pure diesel combustion (D100), a ternary blend of diesel-treated waste engine oil (TWEO)-butanol (60:20:20-DWB20), and a ternary blend of diesel-TWEO-octanol (60:20:20-DWO20). The waste engine oil was improved by acid-clay treatment, allowing it to be used in the fuel blend. Key findings revealed that incorporating butanol and octanol into the treated waste oil–diesel blends produced in-cylinder pressure and heat release rates comparable to those of pure diesel. Additionally, CO 2 emissions were lower for the octanol-containing blend at lower pedal positions, while the butanol-containing blend exhibited reduced HC and NO X emissions compared to pure diesel. The outcomes of this work are pertinent to the efforts of renewable alternative fuels in the pursuit of clean and effective combustion technologies for future powertrain systems.