If you’re suddenly experiencing a low FPS on a video game that your PC was able to run in the past, then the issue could be your CPU temperature.
More specifically, it may be your thermal paste—or lack thereof.
Common symptoms include an unexplained drop in framerate, a noisy CPU fan, and downgraded graphics. In many cases, it can make the game unbearable to play, even with the graphics on low.
To diagnose the problem, you will need to download HWiNFO or Speccy. These free programs will provide you with system information about your PC. More importantly, they will give you with a real-time temperature reading of your CPU, graphics card, and hard drive.
Your CPU temperature should be about 30–50 °C while idle (doing nothing). If it is reaching 60°C or more while idle, then you may need to replace your thermal paste.
Generally speaking, you will need to replace the paste every 5–10 years. However, the rate at which it degrades depends on factors such as the quality of the paste and the intensity of the tasks that your PC performs. For example, if you’re a frequent gamer, then you may find that you need to replace it every 2–3 years.
Degraded thermal paste will look powdery and chalky, almost like it is beginning to crumble. To replace it, you will first need to dampen a lint-free cloth with rubbing alcohol and then gently remove the old paste.
Note that putting new paste on top of old paste will not work. That would defeat the purpose.
Once the old material has been wiped away, place a pea-sized blob of new paste on the CPU and then spread it across the top using a plastic gift card or something similar.
After closing the case and restarting your PC, you should notice that the temperature has dropped considerably.