Can I Reuse an Opened Tube of Thermal Paste?

Check your CPU temperatures with a hardware monitor first. If the temperatures are within the processor’s normal limits, there is no immediate reason to panic. An opened tube is generally fine to reuse if it was capped properly and the paste still comes out smooth rather than dried, separated, or gritty. Still, because the cooler was removed without fresh paste, I’d clean the old material off and remount it with a fresh application. A 9800X3D reaching around 95°C in a heavy Cinebench workload can be normal because it may reach its thermal limit, especially if temperatures are much lower during ordinary use.

Thermal paste does not need to be treated like food with a strict single-use deadline. A properly sealed tube can remain usable for years; one person has even used a tube of Arctic Silver 5 after more than a decade. Inspect it before applying it, and replace it if it has dried out or changed consistency. The important part is applying new paste whenever the cooler is removed, since disturbing the existing layer can create air gaps and uneven coverage.

The temperature readings matter more than the age of the tube. Around 50°C at idle is fine, and roughly 95°C during an all-core benchmark is not automatically dangerous for that processor. If you want peace of mind, use the old paste only if its consistency is still normal, then monitor temperatures again after reinstalling the cooler.