I had an 87 GTA with an L98 and 3.27 gears and it got pretty good mileage on the highway. cruise at 75 at about 2100 RPM, right in the torque curve 8) . around town it was a little worse. I would guess the mileage around town to be around 16-18 if I could keep my foot out of it (that never happened). But on the highway, I could knock down 24 pretty easily because I never had to push the skinny pedal too far to pick up the pace. GOD DAMN I MISS THAT CAR!!!!