thermostat

[michael]

There has been a thread on thermostats already some time ago.
I have had a cold running car for a few Winters.  I replaced the  
thermostat a couple of times with no change.  (It was not the sensor,  
the air from the vents was cold.)
I tried it again this Winter with no change.  I purchased an after  
market 192º thermostat and it solved (?) the problem.  The only  
thermostat sold by Audi for this car must be a cooler one.
Until last night.
On a 12 mile trip, the coolant was cool.
On the return 12 mile trip after sitting for one hour, the coolant  
was normal.

What am I missing here?
- Michael