Purpose: To comprehensively consider the effect of bioethanol as an additive to gasoline on the operational properties of transport engines from the point of view of their differences in physical and chemical properties and technologies, taking into account not only advantages, but also disadvantages. To more profoundly evaluate the volatility of gasoline-ethanol mixtures at different ethanol and water contents, and its effect on startability. Methods: Comparison of available data in normative and reference literature, also in scientific publications. Conducting an experiment using the standard method for gasoline to measure the saturated vapor pressure of gasoline-ethanol mixture of various composition. Results: From the collected data, parameters of the gasoline-ethanol mixture that are important for operation of transport engines have been identified. The need for a detailed assessment of the influence of the composition of such mixtures on the structural materials of transport engines has been identified. Data have been obtained on the volatility of mixtures in a wide temperature range, simulating real operating conditions. No significant deterioration in startability has been revealed. A visible violation of the phase stability of mixtures containing more than 7.5% water has been noted. Practical significance: The measured degree of volatility and startability of gasoline-ethanol mixtures of the various composition allows us to conclude that their level in comparison with gasoline, for mixtures with a 5% ethanol content is satisfactory, and for mixtures with 85% ethanol, is relatively satisfactory. For the first time, the parameters of the provided standard procedure are expanded, relative to the usual temperature recommended when measuring the vapor pressure, to possibly wider limits, allowing a more complete picture to be obtained.