Oil? Synthetic, blend, or conventional

I am coming up on my first oil change. I will most likely do it after the break in period before 3000 miles. I was planning on using mobil 1 5-30 synthetic. You can buy a 6 pack at costco for 24 bucks. The manufacturer specifies 5-30, but the dealership says they use Penzoil synthetic blend. What do you guys use on your 350's and G35's? I used to use Mobile 1 on my truck. Is it worth it? Lets discuss the brands, synthetic versus conventional, What does everyone think?

I have used synthetic oils since 1973 and that was Amsoil. I have used Mobil One in vehicles for years now with no problems. I have heard bad stuff on Mobil One so was thinking about trying a different brand. I need to use the new 5-20W in my Mazda3 so it is harder to come by. What did you end up using?

All newer car from th '90's up are designed with SYNTHETIC oil in mind... personaly I would not put anything else but synthetic in your car!

Whoops... old thread... sorry!