Mobil 1 5W-30 full synthetic in my GTI. Last time around I used Mobil 1 Extended Performance (15,000 mile synthetic) because I put a rediculous amount of miles in my car (150+ per day), and changed the oil at around 13,000 miles (a little under 3 months), and the oil came back from Blackstone Labs telling me that I could actually go longer without changing my oil. This time I went with regular 5W-30 synthetic because I commute to work in a vanpool (over $600/mo savings in gas), so I will probably change next for time, not miles.