I really wonder what these cars would do with some high tire pressure. I put the tires in my Camry up to 40psi cold. It's louder, and not a smooth, but the car appears to be getting better MPG than the tires at ~36psi.
I think I generally run my tires on the GVR-4 at 28-32 psi or something like that. I've never experimented with higher tire pressure. I'm going to look into pumping them way up for the next long drive I take.
The other thing that bites us is that most of us have relatively low compression engines. Stock is 7.8:1, and the high end is generally 9:1 for built motors. AND we are fighting the AWD drive train.
My mom's 2007 VW Passat 2.0 TFSI on the other hand gets 30-35mpg on the highway. Granted it is much newer, is FWD, has FSI, but I think the 10.5:1 compression helps a lot.