The invention relates to the use of polyorganosiloxanes having 3 or more siloxane units, which have one or more organic fractions R1, where R1 has one or more carbon-carbon multiple bonds and at least 4 carbon atoms, and wherein the presence of hydrocarbon fractions having a chain length of 5 to 50 carbon atoms is excluded, as additives in the processing of rubber. The polyorganosiloxanes are used in the processing and vulcanization of rubber in a quantity of 0.1 to 10 phr and incorporated by reaction in same. Said polyorganosiloxanes produce a reduction in the viscosity of the rubber during processing and optionally an improvement in the mechanical properties of the vulcanized rubber.