PurposeTo prolong engine life and reduce exhaust pollution caused by gasoline engines, the aim of this paper was to compare the lubrication properties of biofuel (ethanol) blends and pure unleaded gasoline.Design/methodology/approachBiofuels with a concentration of 0, 1, 2, 5 and 10 per cent were added to unleaded gasoline to form ethanol-blended fuels named E0, E1, E2, E5 and E10. Next, the ethanol-blended fuels and unleaded gasoline were used to power engines to facilitate comparisons between the pollution created from exhaust emissions.FindingsUsing ethanol as a fuel additive in pure unleaded gasoline improves engine performance and reduces exhaust emissions. Because bioethanol does not contain lead but contains low aromatic and high oxygen content, it induces more complete combustion compared with conventional unleaded gasoline.Originality/valueUsing biofuels as auxiliary fuel reduces environmental pollution, strengthens local agricultural economy, creates employment opportunities and reduces demand for fossil fuels.