I just purchased a 2011 wrx and i just noticed this right now. I drove the car for about 10 mins to the gym then turned it off and went to the gym for about 1 hour.
After coming back out, I turned on the car and I noticed the coolant temperature was a little warm a little and I drove for about 10 mins and it was at operating temperature... So i decided to drive a little spiritedly and i noticed the coolant temperature gauge dropped a little below the middle mark (about 1 increment from the middle)towards the C. I turned off the car and turned it back on and it went back to the middle... Can anyone explain to me why this happened and if I WOT 10 min after driving, will it cause any damage? I did a quick search prior to creating this thread and found out it can be air bubbles? but nothing about damaging the car or what not... Needless to say the car has passed the 1k mile mark.