The problem is you still get poor average mpg. If you live on a freeway and rarely drive in town then you have a point but quoting hwy only mpg numbers is false advertisement. It's like all these new compact cars claiming hybrid-like mpg by quoting hwy only mpg when in reality they are only good for 30mpg-35mpg average. A hybrid like the Prius is good for 50mpg average.
I 'mnot slamming your car. I raced a 2000 Trans AM, a 2000 C5, and an 800hp GMC Sierra before buying my Prius. While my TA could pull 30mpg on highway trips it was still only a 24mpg car on average. Well before the 4400 stall and piglet cam. lol
You could always try some fuel economy mods like narrower LRR tires but they wouldn't be useful when you decide to drive like an asshole.
However, driving using hypermiling techniques can't dramatically improve your mpg without spending any money or ruining performance.