I can average 39.2mpg at 62mph CC @ 75F. Road is pretty darn flat with some tiny ups and downs here and there. No Wind. This is with 3/4 of the tank filled and I myself weigh about 218 lbs - theres absolutely nothing else in the car (I travel as light as possible). I have found that at 60MPH cruise the car does slightly worse than at 62 (or my spedometer is really that far off...) and at 65 its a whole 1.5 MPG lower. Go up to 70, and MPGs drop to about 35. Never tried a test with under 60 as I am afraid that some angry driver will shoot me (literally, it does happen here in Cali...)