[mpg_numbers_guy]

I know it's not apples to apples, but someone on here averaged 44 MPG out of an old Chevrolet Caprice with some ecomods, and what is probably the tallest geared transmission out there. Cruising speeds were between 700 and 1300 RPM in top gear if I remember correctly.

As mentioned lighter, more aerodynamic wheels, skinnier low rolling resistance tires, etc. all help.

Rather than upping the compression I would try to tune the car for lean burn. Lean burn is worth a good 15%-20% improvement in fuel economy, depending on how lean you car can handle.