i would think 17-18 mpg and low 14's without the rumble of a large cam/headers is very doable. I haven't checked my gas mileage yet, but i would guess I'm around the 18 mpg mark with my 360 Duster. Actually, i'm going to go to 2.94 gears eventually, because the 2.45's are just too tall, and my car really will never see a interstate. I think just 2.94's without any other changes puts me easily into the 13's.