I've got a 2002 Grand Am (3.4L V6) with almost 99,000 miles on it.

I recently switched over to synthetic oil (Valvoline Max Life
Synthetic) b/c i had a coupon from vioc and figured i'd try it out.
Now, i've gotten it a couple of times, but i haven't noticed any
increase in mpg.  Actually, i've noticed i've lost about 1-2 mpg on
average over what i was getting.  What would explain that?  Seems to
have been getting better lately though.

Anyway, now I'm thinking I don't require synthetics in my car, b/c it
doesn't haul anything and I live in Missouri which doesn't get
temperatures that are TOO extreme.

Is it harmful to my engine to switch back to the Conventional Max Life?