I use Mobil 1 5w20.. only thing I've heard which seems to be true regarding swapping to synthetic, is to allow the motor to break in with regular oil, then switch. I switched at 6k, some switch at 100k, blah blah .. works fine.. $4.99 a quart.
I don't buy any myths about switching to "blends" before swapping to full.. I've switched my '04 over, my 130k mi '88, and a 165k Jeep straight from petrol oil to synthetic, no probs.