I'm not a guy but...

lowest I've ever gotten was 15.6 mpg but I generally average around 17 with very very little highway driving. My way to work involves only secondary highways. I'd get up to 20 mpg with highway driving with an average 19-20 (likely with some screwing around with lower gear pulls for S&G). I've gotten as much as 22.5 mpg at 100% highway with the cruise set.
I love the GTO and G35C but I'm sure if I drove them they wouldn't feel even close to as comfortable as I am now. The 8 just
feels right... I knew that was the car for me as soon as I sat in it. And the insane amount of RPMs makes up for a lack of power. I never get bored driving it.
Have to agree with Gary... lack of a spoiler on an 8 makes me feel weird.. sorry James