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The thermal paste is supposed to facilitate the transfer of the heat from the CPU/GPU to the heatsink. This only works efficiently if a thin layer of thermal paste can be applied between CPU and heatsink in such a way that minimises the chance of creating “air bubbles” (air has a bad thermal conductivity) If you are experiencing the same kind of heat-related issues with your own MBP, and want to try and reapply the thermal paste – provided you are well aware that this will virtually void the warranty, if any.