Can any one help, I have a 58 reg Q5 SE Tdi Auto and I am having a oil smell coming from my car when I stop.  About 7 months ago my husband thought it would be a good idea to have the gearbox oil changed by a gear box company and the air conditioning pumped up as we were due to go on a long journey.  Shortly after that I noticed a oil smell every now and then when I stopped driving e.g. waiting in traffic.  I took the car back and found that one of the screws was not tight enough and the oil was slowley leaking.  This was fixed and all was OK.  Then a few months later every now and then I got the same smell.  It did not happen every day but was noticeable when I stopped.  If I changed the Air intake onto inside only it stopped.  The car has been checked and there are no leeks to the engine or gearbox and it drives perfectly.  I have also been speaking to the gearbox company who have had the same problem with another customers Q5 and they can not find the fault.  The only suggestion is to replace the gearbox oil with genuine Audi oil incase it runs at a different temperature.  Has anyone got any other thoughts of what might be causing the problem ?

Could be DFP regeneration? This can sometime have a strong smell to it but is perfectly normal.