There have been some interesting posts in this thread, so here's my $0.02. The techniques that have been mentioned do work in my 07 HCH. I've had 55-58mpg per full tank for six months now driving 45 miles per workday. I keep the tire pressure around 40psi and check it weekly. Maintenance is done at the dealer (part of the purchase). I don't use cruise control and avoid using the A/C while accelerating onto interstates and climbing hills. Recently I noticed that FE doesn't drop with windows down at 55-60mph but it definitely drops when the A/C is on. The 1,100 rpm acceleration works well on residential streets with light traffic. I'm no MSantos, but I think I've had good mileage long enough to say it's not a fluke. Best of luck... and the best part is that it still drives like a Civic (had a 98 EX that lasted 149K with 40mpg highway).

Keep smiling,