The purpose of the invention described in this document is to disclose a novel method using mixtures to change the viscosity of both light and heavy petroleums, by decreasing or increasing said viscosity. The methods derived from this invention are useful at ambient temperature and atmospheric pressure. The active component of the invention is dopamine, a compound that combined with other substances enables a change in the fluidity properties of petroleum, an increase in the electric charge properties of the mixtures and solutions and the dissolution of insoluble compounds in water or aqueous solutions. Some of the mixtures of this invention have been applied to modifying proton mobility, whereby significant increases in particular caused by the presence of metals chosen to bring about this purpose, can be detected within these mixtures, by measuring the electric charge. The experiments which led to this invention demonstrated that the juice obtained from any part of the banana plant, whereof the chemical analysis includes dopamine and other compounds such as quinonas, carotenes and terpenes, is the cause of the effects found, in particular effects on the electric properties and on dissolving metals and metal compounds.