My dipstick has been fitted to my S4 since I bought it, 2.5 years ago, the plug thing is kept safe in a poly bag along with the wheel nut covers removal tool and the security key for the wheel nuts - in the net storage area in the RHS of the boot space - I do remove it when submitting the car for servicing though. There used to be lots of warnings about these dipsticks melting coming from USA, but I seem to remember that USA was probably late in getting cars fitted with plastic dipsticks, I think that TDI engines got them first and they were not too popular in USA. Plus, I think that there was at least one VAG engine where the guide was shortened coincident with not fitting a dipstick - that also generated some internet misinformation.
