I drove a 00 gt with 171k, and one with 140k, both got 33-35 mpg going 55 down highway at 1800 rpm. Ive had 5 or 6 gps now, and they all gotten over 30 if i tried, even my 05 comp g. I had a 98 gtp with 210k and it got about 29.

I got 27 mpg going 75-80 on a 400 mile trip. in my 01 gt with 63k miles