I recently upgraded from a Pentium Gold G5400 to an Intel Core i5-8500. Since the upgrade, idle temperatures sit around 60°C, and launching Overwatch 2 makes the CPU fan ramp up aggressively. HWiNFO showed the processor reaching about 90°C, which never happened with the G5400. My system has a GTX 1050 Ti Low Profile, 32 GB of Corsair Vengeance LPX RAM, and Arctic MX-4 thermal paste. I believe I applied enough paste. The computer is a compact HP Envy? Flex Pro C-style system using its original medium-sized cooler, so I'm wondering whether the cooler is mounted correctly or simply insufficient for the i5-8500.
2 Answers
First check that the cooler is fully secured. If it uses Intel push pins, make sure all four are locked and the heatsink is sitting flat on the CPU. A poor mount can easily cause high idle and load temperatures. Also verify that the CPU fan is connected to the CPU_FAN header and is spinning normally.
The original cooler may have been adequate for the lower-power G5400 but not for the i5-8500, especially inside a compact prebuilt case. Around 90°C during a demanding game is hotter than ideal, so the cooler or case airflow is probably the limiting factor. Reinstalling the cooler with a small amount of thermal paste could help, but you may ultimately need a better low-profile cooler that fits the chassis.

That makes sense. It is a compact system and I’m still using its stock cooler, so it may simply not be capable of handling the upgraded processor. I’ll check the mounting and look for a compatible replacement before changing the whole computer.