[klagermkii]

As a more reliable way to confirm if you have some thermal problem on an older Mac, download and run Intel Power Gadget. That shows the current frequency of the CPU, and when combined with running some program that puts all cores under load, you can see if the frequency drops below what is designed for.

Be aware it isn't always thermal paste that is the culprit. I had a 2012 Retina 15" MBP that was normally 2.6GHz but would drop down to 1.4GHz. That was purely due to the fans and (tiny) vents getting choked up. Solved by opening and using compressed air to clean, no fiddling with CPU paste.