rpadam: Yes ive just had the same problem with the Mobil 1 OW40 as it doesnt say 503.01 on the back anymore.
Although check this out as it says ExxonMobil says its compatible with VW503.01:
Mobil 1 New Life 0W40 Fully Synthetic Motor Oil 5L
Mobil 1 New Life 0W-40 Fully Synthetic Engine Oil
Si I needed an oil topup and ive called allparts and had a nice discussion about this over the phone. (also managed to get them down on their price to match that of the websites which was very nice of them.
Once i got there, another lad who had a special interest in audi S3's said he would recommend this oil, and that yes they did change the name but its going to be fine and could even improve fuel economy very slightly over a longer period....
So ive bought it....and ill keep you guys informed (currently getting 34 MPG) on a 2002 audi s3 8L 225 BAM