So one day I'm driving my car and its coolant temperature is normal. As I continue to drive, I notice that the temperature is becoming cooler. Then, the needle goes up again after some time. My car had a cold-valve done to it last year but I think this has something to do with a thermostat...what do you guys think?

 

Keep your car about 4k rpm everywhere you drive

 

its your thermostat i had the same problem with my volvo it would warm up stay at the middle then it would drop to about 1/4 and stay there sometimes even drop down to zero lol , but i replaced it cost me around $30cdn for the thermostat from a volvo dealership, should be around the same price for audis

 

my car did that when i got it.. i forgot what they changed but it was about 40 bucks at the dealer.. not a bad problem