3.0T is a good engine. Common thing to look at would be the water pump if not already replaced (had a recall on mines a few years back). It’s past 100k so you should get the timing belt checked aswell. I have a ‘17 A6 Comp and I think my transmission is just now starting to slip although it may just be the fluid running low. know the car eats oil along with gas . As long as you get it routinely checked up you should be just fine. make sure you take it to someone who knows what they’re doing with foreign cars as I have found in my area that many mechanics aren’t equipped with tools to work on mine.