Ethanol–Gasoline Blends: A Comprehensive Review on Fuel Properties, Engine Performance, and Emission Characteristics

Abstract

The increasing global demand for energy, coupled with the depletion of petroleum reserves and environmental concerns, has necessitated the search for renewable and cleaner fuels. Ethanol, derived from biomass, has emerged as a promising alternative fuel or additive for spark-ignition (SI) engines. This review synthesises results from several experimental studies that investigated the effects of ethanol–gasoline blends on fuel properties, engine performance, and emission characteristics. Across the reviewed works, ethanol addition was found to improve octane rating, enhance combustion efficiency, and reduce carbon monoxide (CO) and hydrocarbon (HC) emissions. However, ethanol’s lower heating value led to increased fuel consumption at higher blend ratios. The majority of studies indicated that moderate blends, particularly E20 (20% ethanol, 80% gasoline), provide an optimal balance of engine performance, thermal efficiency, and emission reduction. This review emphasises the potential of ethanol–gasoline blends as a transitional solution towards sustainable transport energy systems, while also highlighting challenges related to water miscibility, aldehyde emissions, and the need for engine modifications at high ethanol concentrations.