Pascal wondered about changing his oil seals as a precaution.  I'll admit straight off that I don't know the right answer (sorry Pascal), but I did have a little experience of this.

  I had a 12 year old Golf (Rabbit) Cabriolet and the gearbox failed at 100,000 miles; this is a well-known problem with the 5-speed transmissions on the higher-powered engines but, as with most well-known problems, it only became known to me after it happened.

  Anyway, to make a long story boring, after the transmission shop pulled the box, they noticed the beginnings of a weep from the main crank oil seal.  They replaced it and found the leak was worse than before.

  It appears that the hard rim of the old oil seal had actually worn a groove into the crankshaft.  They solved the problem by removing the the seal and putting it in backwards so that it bore on a fresh part of the crank.

  Just my E0.0154 worth (at current exchange rates).

  Niall