Tailpipe smoke

[vai]

'04 Cayenne S, Stopped at gas station to pump gas, as pumping noticed thin vapour/smoke from left tailpipe, I thought I had left the engine running as that is the kind of emission I see from the tail pipe with engine idling. Finished pumping and went to the front, the engine had been turned off! so this was coming out with the engine off. The continues to drive fine! Any ideas?

[RFM]

It's the residual vapour which comes out of the exhaust, a normal phenomenon under some circumstances (engine temp.-outside temp. and humidity) Filling gas should always done with the engine off, to prevent emission fault codes and not to confuse the control box (DME - actual consumption/engine running versus actual fuel tank contents while filling up)