<p> This study investigates how the composition of hydrocarbon isomers affects the physical properties of surrogate e-gasoline, with a focus on its potential role in synthetic fuel formulation. As interest in carbon-neutral fuels grows, surrogate e-gasoline has emerged as a promising alternative to conventional options. A predictive program was developed to estimate key fuel properties—including density, vapor pressure, and octane number—based on varying ratios of paraffins, isoparaffins, and naphthenes, incorporating chain growth probability derived from Fischer–Tropsch synthesis. The results show consistent trends between isomer composition and physical properties. For example, isoparaffins tend to improve octane number, while naphthenes contribute to higher density but lower vapor pressure. These trends suggest that adjusting isomer ratios can help achieve fuel characteristics suitable for intended applications. Overall, the proposed approach provides a framework for designing synthetic fuels with properties aligned to the needs of internal combustion engines and low-emission targets.</p>