My thoughts or rather comment is based on
Castrol Syntec 10W-30:
I guess I don't want to repeat what others have said about the advantages of using Synthetic oil, but here is what I want to add which is really nothing.

Just before going back to Castrol Syntec synthetic oil, I let my dealer change oil on the part of the 30000mile service. I really didn't notice anything drastically different until I change out the conventional oil and went back with Castrol Syntec.
Other than the fact that my car running better it seems that with synthetic, my car warms up about 40% quicker than when I had the conventional oil!
In where I live, Northern Virginia, this winter have been mild with temperature ranging from 20-40 but still I am very appreciated how quickly the car reaches optimal operating temperature.
Also this effects in-between start-up, where it warms up even quicker.

Anyway, if you are going past 7500 mile mark, definitely do try synthetic, either Castrol or Mobile(I've used Mobile1 5times and I am giving Castrol a try). You will be very happy that you did especially in the winter time.

 

Me too, I've noticed that the car warms up faster with the Mobil 1 synthetic

 

I've been using synthetics (mainly Mobil 1 but a short stint of Amzoil when I lived in Iowa and Mobil was nowhere to be found) since the late '70s. I can't say that I've ever noticed a faster warmup and I would submit that it's counterintuitive since there would theoretically be less viscous drag on the moving parts. Less drag = lower temperatures and a slower temperature change gradient.

Maybe I'm missing something but I don't hink so...

 

I have not yet switched to synthetic on the S2k because of the mileage but in my dailiy driver when I switched to Mobile 1, I noticed that the car idled more smoothly.