Just drove #830 from Detroit to Tampa and noticed that the fuel economy seemed to vary with each tank of gas. When I started out it had 750mi on it and I changed the oil at about 550mi. I usually maintained between 75-85MPH. All fill-ups were 93 octane, the first tank I averaged 23.5 MPG, the second about 24.5 MPG but the third tank yielded 28.5 MPG, and the final tank was about 26 MPG. The terrain was different so there should be some difference but the 3rd and 4th tanks were through Georgia and Florida on basically flat terrain. Has anyone else noticed this. Also I noticed that the a/c remains on even if the a/c light is not on but the recirculate light is on. Is this correct or is it malfunctioning?