Pontiac G8 2008-2010 - Whats a near stock gt get for mileage?

I'm sorta thinking about replacing my wife's Bonneville GXP with a G8 GT and wondering about the mileage. It would probably stay relatively close to stock. Maybe a cat-back and tune at the most. So what is everyone getting for milage?

stock i got 17 city. 29 highway. but cruising at 45 with cruise control i got 45mpg.

Stock mine got 21 city and 26 highway. After tune and vararam CAI, it gets 22-23 city and 27-28 highway! Either are awesome for the performance of these cars!!!

Wife's car gets 16 - almost all in town driving.

Thanks for your input guys.

Fully modded my car gets about 12-14 city and 23 on highway.

19 city/ 21hwy (80mph cruising speed )
Vararam/Cortex and the cylinder thing what the hell do you call it turned off

11-12 city and 20-22 hwy @ 75. See sig. for details on G8 mods.

Those are some good numbers for such a big powerful car!