I'm a new owner of a used 2007 A3 2.0 DSG S-Line ..

I think I may have a problem with my cooling system, in particular I believe the thermostat is not closing completely. It seems to take forever for my car to get up to temperature. In addition when descending from the mountains I've seen my temp gauge drop from normal temp to full cold. To me these symptoms indicate a thermostat that won't close completely.

Anyone else heard of a problem like this? I'm bringing it in to the dealer next week but I like to know whats wrong myself.

Other questions:

When I back out of my driveway, stop, then put the car into drive I usually get a very loud noise (groaning or grinding type of noise) when forward motion begins. I can't really tell where the noise is coming from... Anybody have this issue?

Why did Audi choose such odd gear ratio spacing on the DSG? In particular it feels like the jump between 3rd and 4th gears is quite large when the ratio difference in the higher gears is very small...

I just put a set of Dunlop Wintersport 3D 205/55 16 on black steelies on the car for the winter... I think it looks fantastic as I look the industrial look of steelies and I don't like the look of super low profile tires. I'm old enough to remember when people thought 60 series tires were low profile. I frankly don't understand what the fascination is with such huge wheels... The ride is much improved on these tires over the stock P6 tires.

Thanks,
Jeff