Got advice to buy the plastic cover that is right under the engine since mine is gone. But I still don’t see how this would help the car to reach 90c, maybe 70c but not up to 90c. The car only reaches 90c on long trips on highway. When I drive at least 100km/h but as soon as I slow down it drops again no matter if it’s -20 -5 or +5 outside. I have bought the car three months ago so I don’t know if it’s been like this for a while or something recent. I have owned a4 b8 2.0tdi, a6 c6 2.0tdi, audi a4 b6 1.9tdi, vw sharan/caravelle, audi q5 2.0. None of these had any problem to reach the operating temperature no matter the outside temperature. No mechanic has any idea but different small things that I could change and see if it helps.