I have been averaging in high teens when I am squirrling around, but on a trip down south I ran through a tank of gas with cruse control at 75 mph with the top down, I got 29.6 mpg on that tank, I was very impressed.
Ed
2000 2.7L Boxster
Arctic Silver/Black, 50K
TTP intake/headers/high-flow cats
AutoThority performance chip