Abstract: The present invention relates to the use of a chemical composition to modify the physical properties (viscosity and interfacial tension) of heavy and extra-heavy crude oils, to increase their mobility. The chemical composition comprises or consists of a combination of systems based on ionic and non-ionic liquids, which may be pure or modified, mixed in an aqueous or organic medium as a dispersing agent, depending on the nature of the crude to be treated, together with a surfactant. The composition is mixed with the crude oil at a temperature between 5 and 100° C., at pressures from 1 atm (14.7 psi) up to about 680.2 atm (10,000 psi). The composition can be mixed with heavy crude oils, at the point of extraction from the well in the field, during the transport of crude oil in pipelines, or in the well discharge pipelines.