Actually Premium gas is about $.30 to $.40 more expensive than the 87 octane. with a 20 gallon tank, a fill up with premium is at most $8 more.
That being said, for our trucks premium is a waste of money, my 4.0 runs fine on the cheap stuff.
Now on my 2004 Nissan Maxima, it is recommended that you run 91 octane fuel, and while it does run on 87, the gas mileage suffers enough that the $8 difference in price of a fill up is justified.
As for premium memberships good job and I really need to get one of those...
AJ