Yea you're right about the change intervals to some extent. Looking them up now, most synthetics are only about 7500 miles, so I partially take back that earlier statement. <img src="/forums/images/graemlins/baby.gif" alt="" />
But, many synthetic manufacturers are coming out with "extended performance"-type synthetics that do have those longer change intervals, including Amsoil and Mobil 1. I could've sworn Amsoil used to make some crazy 10 or 15k oil (I don't know if they still do), but it was super expensive! But if not, then I was dead wrong.

My girlfiend's Acura calls for something like 7500 miles between changes, but I don't know if they're using synthetic from the factory or not.

OEM recommends the 5W-30 and it does get better mileage (supposedly), but my biggest thing is that I wouldn't put all my faith in super-thin dino oil in a 115-degree desert environment! Especially if -- like me -- you tend to run a little over 3000 miles between changes.

In my own humble opinion, the synthetic will be far superior to dino in the long run, whether it's changed at 3000 or 7500 miles. Just my opinion though <img src="/forums/images/graemlins/drunk.gif" alt="" />