thermistor and heatsink compound

[pcmad]

I've just bought a new thermistor for my 3-D printer hot end the previous person who owned the machine put heat sink compound in the hole where the thermistor is located does this contaminate the sensor and give false readings or should that be fine please bear in mind that there is a 2mm bear wire gap from the sensor to the start on the insulation

please not if a was to use heat sink compound it will be the white stuff

[richnormand]

I have used silicone based white stuff before for both my 3D printer and thermistors for temperature stabilised diode lasers so I would assume you are OK.
The real issue would be to use some electrically conductive compound like the silver or copper based stuff that would shunt the thermistor and give a lower resistance reading.
Other thing to look for is that thermal compound tends to dry and cake so make sure the hole is clean and allows the full insertion of the new thermistor.

[TimFox]

The "white stuff" is usually aluminum oxide, zinc oxide, or similar powder in the silicone vehicle that is a good electrical insulator and decent heat conductor.  It shouldn't contaminate the sensor.
A data sheet:  https://www.mgchemicals.com/downloads/tds/tds-860.pdf