The design of cyber-physical systems is a complex process and relies on the simulation of the system behavior before its deployment. Co-simulation allows system designers to simulate a whole system composed of a number of interconnected subsystems. Traditionally, these models are modeled by experts of different fields using different tools, and then integrated into one environment to perform simulation at the system-level. This results in complex and heavy co-simulations and requires adequate solutions and tools in order to reduce the execution time. Unfortunately, most modeling tools perform only mono-core simulations and do not take advantage of the omnipresent multi-core processors. This paper addresses the problem of efficient parallelization of co-simulations. It presents a multi-core scheduling heuris-tic for parallelizing FMI-compliant models on multi-core processors. The limitations of this heuristic are highlighted and two solutions for dealing with them are presented. The obtained speed-up using each of these solutions is illustrated and discussed for further improvements .