I'm looking to buy a 2006 A3 sport 2.0 Tdi with 92000 miles at £3999. Is this a good buy or not. 

It all depends on condition, and you are the only one who can assess that.

The condition is good, I've a mechanic say that it is a bad year for the A3 but I though I would ask someone who has one possibly. 

Hello Ben,

Ask your mechanic why he says 2006 is a bad year? Re. the car you are thinking of actually buying- service history? How long has the last owner had it? Are you going to contact him/ her to find out more about it before you buy ( assuming this is a trade sale rather than private)? Never buy without doing that - it's the best way of finding out what is wrong - if not buying it directly from the owner. 

N, I and prices? Don't know, but you should be able to research what is available locally as a comparison. Part exchanging against it? It all makes a difference. As I understand it all MOTs over there are done at VOSA type stations ( similar to HGVs here?) rather than at MOT stations, so the uniformity of assessment should be better than over with us. 

Good luck with whatever you decide.

Kind regards,

Gareth.

In your position Ben, I would find out what is wrong with it, (all s/h cars have faults in my view,) get the costs to put right anything you can't live with, add those costs to the purchase price, and then assess if you can or want to spend that much money.