Part of CREATE-GV’s Mercury, the Powertrain Analysis and Computational Environment (PACE) is a simulation tool that provides advanced behavioral modeling of the powertrain subsystem of conventional or hybrid-electric vehicles. PACE performs its task by converting an existing powertrain architecture created in Autonomie or Matlab/Simulink into HPC-ready C++ code using an automated code generation capability, which parses the powertrain model’s Simulink XML files. Utilizing PACE’s modular powertrain model structure, a Simulink lumped-mass thermal model has been developed separately to augment the original functionality of the powertrain model. The augmented powertrain model was then subjected to a high-fidelity max speed test in Mercury’s simulation environment to demonstrate the successful integration of a ‘3rd party’ component via the PACE module. The Mercury Driver Client was also modified to accept calculated temperatures as an input. Including thermal analysis in powertrain modeling is crucial for vehicle development, especially hybrid-electrics. The lumped-mass thermal model provides a first-order estimation of the thermal behavior, but the modular structure of PACE and (ultimately) Mercury allows more sophisticated models to be easily integrated.