I built my PC about four or five years ago, and its performance has gotten noticeably worse. The CPU seems to sit around 70–80% usage much of the time, so I'm wondering whether I should reinstall the operating system because of background software or possible malware. Before doing that, I'm considering cleaning the system and applying fresh thermal paste. How often do you usually replace it, and could old paste explain these symptoms?
5 Answers
Thermal paste usually doesn’t need to be replaced on a schedule. If the cooler is removed, or temperatures have become unusually high after cleaning the case and checking the fans, then repasting makes sense. Good paste can last five to ten years or more.
Make sure you’re separating CPU usage from CPU temperature. A reading of 70–80% means the processor is busy; 70–80°C means it’s warm. Neither one automatically means the thermal paste is bad. Check Task Manager to see what is using the CPU, especially when the computer is idle.
If the system is constantly using 70–80% CPU while you’re just sitting at the desktop, look for background programs, updates, unwanted software, or malware. Repasting won’t fix high usage by itself. Check temperatures, clock speeds, and which processes are consuming resources before changing anything.
Some users replace paste every year or two, but that’s more of a personal maintenance habit than a requirement. A decent application can remain effective for many years, and a temperature comparison under the same workload is more useful than replacing it just because the PC is old.
Most people only repaste when replacing or removing the cooler. Clean dust from the case and heatsink first, confirm the fans are working, and then test the temperatures under load. If you do repaste, clean the old compound with isopropyl alcohol and mount the cooler evenly.
When comparing temperatures, also account for room temperature and make sure the workload and fan settings are similar. Otherwise a small difference may not mean anything.