Diesel up to max. 15,000€

Hello, first of all, I don’t think I’m right here in the “Financing” area, because I want to hear more experiences. So please tell me where I can move the topic. I’m currently driving an Audi 80, 2.6L. In the month I return on average 1000km, of which 50% city, which is anything but fun with the fuel prices with my current car. 15L Super on 100km are nothing. In addition, the use on the highway over 140km/h is no longer portable. So I’m looking for a used diesel up to a maximum of 15,000€. Since I’m impressed by Audi, it should be something in the direction again, but also like VW/Skoda etc. My big problem, which car should it become now? I think the 2.0tdi dpf with 170ps is so nice, but I have heard so often about problems beyond the 80,000km. In my price segment, however, the engines have already ~150,000km down. Is that too much for the ‘modern’ engines? If you had an older engine (2 ,5tdi), so also cheaper car possibly less running costs? Although I can not imagine that. My rough preselection is with the Audi A3 Sportback/A4 from BJ ’06 with 2.0tdi 170ps. VW Passat, Skoda Octavia RS also from this year of construction with the engine. But personally the A3 says the most. It should not become a ‘spar wonder’, a certain sportiness and a certain degree of comfort and equipment should bring the car with it. However, I am also off for older models. if they reach the current consumption values somewhat, since 15,000€ is my absolute limit. However, for this I may still be interesting, I often have to say hello to Martin through environmental zones.