Under low temperature conditions relevant to RCCI, combustion is very sensitive to the auto ignition process, and therefore heavily influenced by the detailed mechanism of fuel chemistry. Unfortunately, combustion reaction mechanisms are usually developed sequentially, one reaction at a time, and validated against experiments that often fall outside the range of end-use conditions. Therefore, the chemical mechanism employed may limit the overall fidelity of the combustion simulations. This issue motivates the development of an automatic scheme that generates high fidelity combustion mechanisms for user-selected fuels via large-scale, high-level, a priori theoretical chemical kinetics predictions. This scheme will exploit massively parallel computer architectures to simultaneously calculate the thermochemistry and kinetics of the thousands of relevant chemical species and reactions with high-level quantum mechanical calculations, ushering in the holistic development of mechanisms using the Reaction Mechanism Generator (RMG). The enhanced fidelity of a high level theory-derived mechanism, coupled with uncertainty and sensitivity driven improvement schemes, can directly access arbitrary conditions with dramatically improved and rapidly constructed mechanisms for the end-use conditions. For more information about the exascale computing project, please visit the website: