Hi, I'm new here - I just want to start by saying there is such a wealth of info here, maybe too much so that I'm totally confused =). None the less, by far one of the most informative sites I've seen. I have a 2003 VW Passat 1.8T and I have been using Valvoline SynPower 5W-40 for the last 2 oil changes. I know it's a Group III oil but my car runs super smooth and revs incredibly smooth as well - I have no complaints about the oil. I previously ran Pennzoil 5W-40 Synth and the car was not even close to being as smooth with the SynPower. I know that M1 0W-40 is a Group IV and would like to try it if there were any compelling reasons to switch. And besides, I was reading an Amsoil report on oil analysis and there seems to be good and ok and bad things about all the oil that's out there. So how does one choose??? Valv SynPower, M1, Castrol, Redline, Amsoil - ahhhhhh!!! BTW where does one get Castrol 5W-40 Euro around NYC? Thanks so much for any answers.