NOVELTY - The system (100) has a lubrication circuit (113) and a Rankine cycle working circuit (102) including a shared segment (115), a mixture of Rankine cycle working fluid from the working circuit and lubricant i.e. oil, from the lubrication circuit. A separator (119) receives mixture of the fluid and the lubricant from the shared segment and separates the fluid from the lubricant, where the separated fluid is directed along the working circuit from the separator to a heating zone and the separated lubricant is directed along the lubrication circuit from the separator to a mechanical expander.    USE - Closed-loop organic Rankine cycle system for re-capturing energy from waste heat from a prime mover e.g. internal combustion engine such as diesel engine, spark ignition engine and fuel cell, of a vehicle (all claimed).    ADVANTAGE - The system facilitates heat to transfer from the heated lubricant to the cooled working fluid during the mixing process reducing lubricant temperature to the cooled working fluid temperature. The system allows a mechanical expansion device including interleaved rotors with lobes mounted on a shaft and intermeshing timing gears that coordinate rotation of the rotors and prevent lobes of the interleaved rotors from contacting each other. The system uses a lubrication cooling circuit that maintains the lubricant at acceptable temperature with respect to flowable lubricating oil. The system has reduced sealing considerations and reduced pumping components.    DETAILED DESCRIPTION - The mechanical expander is a rotary mechanical expander (127) or a fixed displacement expander. The separator is a gravity-based separator. The Rankine cycle working circuit is an organic Rankine cycle working circuit. An INDEPENDENT CLAIM is also included for a vehicle.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic block diagram of an organic rankine cycle system with a Rankine cycle working circuit and a lubrication circuit.    Organic Rankine cycle system (100)    Rankine cycle working circuit (102)    Lubrication circuit (113)    Shared segment (115)    Separator (119)    Rotary mechanical expander (127)