There is provided a process, and a device, for the treatment of crude oil, component(s) of crude, or mixtures thereof, to convert components of said hydrocarbon liquid to products having boiling points that are lower than the boiling points of said components prior to treatment. The process comprises subjecting crude to be treated to ultrasound vibrations and to an electromagnetic field emitted by a an electromagnetic field generator; wherein the electromagnetic field emitted by said electromagnetic field generator comprises a component of electromagnetic field modulated by an electromagnetic field emitted from the crude to be treated on the exposure thereof to ultrasound vibrations.