Certainties and challenges in modeling unwashed and washed gums formation in Brazilian gasoline–ethanol blends

[Display omitted] •Robust models are obtained for unwashed and washed gum content in regular gasoline.•The effect of anhydrous ethanol was complex, but it strongly impacted the solubility.•The models from the present study fitted better to experimental data of washed gum.•A better tolerance to change in gasoline composition and ethanol quality was observed. During the gasoline storage, gums are formed by a slow oxidation of some unstable compounds, such as olefins. The high molecular mass oxidation products can become insoluble and form deposits. Its excess affects the injection pattern, the fuel combustion, the durability of the fuel line parts and increases the pollutant emissions. Consequently, a robust knowledge is required to assess better the behavior of the fuel, in particular the impact of biofuels. This article discussed the certainties and challenges in modeling gum formation in blends of Brazilian gasoline with anhydrous ethanol. The impact of experimental and mathematical procedures on the robustness of the model was investigated. They make possible to assess quantitatively the impact of aging period, temperature, ethanol and additive contents in the formation of unwashed and washed gums. The results confirmed the promotion of the process with the increase of the temperature and aging period and showed the complex role of ethanol, strongly dependent on the values of the other factors. Moreover, the comparison with former literature showed that the models from this study were more robust and the dependence with chemical matrix of gasoline and ethanol quality was reduced. Recommendations were given to overcome the remaining challenges.