To anyone that is interested syntec is in fact a group III motor oil and has been since 1997. Prior to that they were a full Group IV pao which they purchased from mobil oil.
In 1999 mobil sued castrol for false advertising. I use the term sued even though it was not a legal court case as we know it, but rather was heard in front of the NAD. National advertising division. They determined that group III oils were refined enough to be advertised as synthetic. The rest is history.
That said, it is important to point out that the German made castrol syntec is full PAO. This is because german laws do not recognize group III as true synthetics. This is the oil that comes in the BMW's and meets their specs. Next time you pick up american syntec read the specs on the back. You will find they don't meet many of the european specs especially the long life specs.
As of today it is difficult to find pure synthetics such as Group IV and V oils and is limited to some smaller companies with the noted exception of the German Castrol syntec which is difficult to find. Even mobil1 one has only small amounts of PAO the rest is group III. I guess they felt if you can't beat them join them.
If you want a pure group IV or better motor oil there is redline and amsoil. For street use Amsoil is probably a better bet. All there oils are PAO based exept their XL line which they openly tell you is group III.
Hope this helps.