manf. due to inadequate thread reach issues. The nipple (threaded thing that filter screws onto) is too short (actually the threads on the filter's baseplate are too recessed) and there may not be enough contact to properly hold the filter to your car. If it falls off or leaks, you could suddenly loose oil pressure and/or most of your oil. In case you were wondering; this isn't good at all for your engine!

recessed too far and the filter may physically fall off or not have enough threads engaged and either strip your nipple (mind out of the gutter...) or leak; often with very bad results.

I use M1 0w-40 with the OEM filter right now (as I am still under warranty). I just had bought several of the M1 filters on sale for my 2.8L 30V Passat and that filter also used to be listed as fittment for the 2.7tt as well.