Lazy termostat?

I just noticed that for a couple of days my temp gauge wont go up to 12. Could it be a slow thermostat that just dont close up completely?

either that, or you have very low compression and the motor is not generating as much heat anymore, our Suburban with 232k on it has this problem now, t'stat is fine.

Maybe your clutch fan is locking up and/or the electric fan switch isnt shutting off from the thermo switch.