I am a new PASSAT owner ('99 GL) and would like to know if anyone has strong opinions about the best oil to use. The car is a 5-speed 1.8T with about 30K miles. I live in North Carolina (current temps are in the 70's, but we should be in the 30's to 50's for the next few months). I do mostly highway driving. In the past, I have used mostly synthetics (Mobil1 et al).