I got my car back yesterday after having its new steering rack and returned the A4 Avant 170 Diesel. After 100miles in the Diesel I got to know the engine quite well. Main points. 170 Diesel Engine is much much smoother than the 140, very very impressed but no patch on the 2.0T. Found the torque band on the 170 way too narrow, pulling out of junctions was a nightmare as you have to wait till the engine hits the torque band, it was almost digital. Its like 'nothing, nothing, nothing then BANG there it all is'! I did feel the extra torque that the 170 has over the 2.0T but it wasnt as smooth or as progressive, when it got going though 50mph+ then it was fine but its the getting up to speed part thats annoying. Overall performance the 170 would be biting at the heels of the 2.0T on a straight line but through corners and through twistys etc I reckon the way the digital torque is delivered it would make the 170 slower. Engine noise wise obviously the 2.0T wins no problem but I was VERY impressed with the quietness of the 170 for a diesel. Still cant get use to the vibration you get through the pedals though. Economy wise I got 30mpg overall over the 100miles, I did give the car a hard time, I reckon if I treated the 2.0T the same way it would give probably 25mpg ish. Overall I liked the 170 engine, better than I thought it would be, Id suggest to anyone that before buying the 2.0T to try out the 170. I currently do 20k miles and yes I would save a lot on fuel costs but the smoothness and flexibility of the engine out weights the extra costs just! I have re-blufinned the car now and boy did I miss it!!!!