Chosen Solution
The CPU in my X240 has been getting up to 90 degrees Celsius and even throttles at times in normal use (youtube, Netflix,etc.), so I was wondering how to replace the thermal paste by yourself?
iwhxtever download the maintenance manual from here Page 76 shows you how to get to the mating surfaces. This guide How to Apply Thermal Paste shows you how to apply thermal paste. Since you are already working on it, make sure the fan is clean and all air inlet slots are clean as well.
