My mom bought a 06 civic lx not too long ago. I made a thread about it. Anyway she has been constantly getting high 20's. So I plugged up the SG2 to her car, calibrated it to her engine and we went for a drive.
On the streets she got 41.7mpg
On the freeway 64mph@65MPG
As long as the car is going 37mph or higher it's very efficient. So we used moderate pedal pressure to get to 37mph and then cruised at about 39-40mph. Coasting before lights was used.