Gas Mileage Experiences?

[JCL12]

I drive an 01 regular boxster with tiptronic.

It is rated for 18/25 (city/highway)

I can get a little over 27.1 MPG on pure highway driving - typical speeds high 70's with a good bunch of 80's and high 60's mixed in with occasional 90-99+.

I am guessing with consistent 68-72mph, I could crack 28 MPG. I think porsche lies about the mpg (or assumes more aggressive diving styles)