Depends on your circumstance, I would say.
If it’s for load lugging, forget the a4 as the 6 is much more accommodating.
For me the whole reason I have had Audi’s is the Quattro (I’m in the sticks in the north of Scotland). They are just so much more planted in the real world conditions.
Next question is economy. If it frugality and space isn’t an issue I would favour a 1.9tdi Quattro a4. The 2.0 frisée apparently has oil pump issues depending on the engine code. I would suspect though that cars of that age have all had the modification to sort the issue in their life.
If frugality isn’t an option and you budget can squeeze you may be able to get your hands on a early c6 3.0tdi Quattro. Can achieve the early 40s on the motor way and long runs but more like just under 30 in town.i had the lemans in black, loved it but I have to say I prefer sitting in my 2001 s6 with the nice recaro leather (it on an lpg conversion which makes it just affordable to run as a second car).
I also had the 2.5tdi in an a4 which was a good desire engine but early models suffered from cam failure (search chocolate cams). Again though if you found an late C5 then this would have been resolved.
Bottom line, there are heaps of options in their, but I would bide your time and wait for the right one with all the spec as there are loads out there
Sent from my iPhone using Tapatalk
