Synthetic is fine. Run it if you feel the cost is acceptable.

If you start the car in very cold weather (-20 F or lower is my mark), then I'd get 0W-40. Mobil 1 5W-30 is pretty good, but the 0W is better when it gets horribly cold.

-Philip Maynard '95 Contour [71 STS | Track Whore] '97 Miata [71 ES | Boulevard Pimp] 2006 autocross results