Lowest I have gotten is 18, highest is 27. I have hit 26-27 several times. Try keeping the car between 2300 and 2700 RPM's because that is where it is most efficient. Since I started watching that, I went from 18 to 20+.






You want to think your selves lucky as here in the UK, gas is about $10 a gallon and diesel is about $12, so it costs me about $120 to fill my 70 Mach1 up
Cheers
Ian