On my commute to work there are a lot of small hills, which I continue to go up and down for most of the drive. The fastest posted speed limit on my commute is 65 MPH not many people stay at that speed. Only a few miles are 65 where the rest is 55 MPH. I have found that maintaining a speed between 62-65 yields the best FE. Soon as I go over 65 unless drafting or going downhill or on flat ground my FE drops. The other day on flat ground and drafting behind a truck I was able to maintain EV mode for about a mile at 77MPH. Even when EV mode stoped I was able to maintain speed and Maxed out FE for a little longer. The road began to change altitude slightly and the truck started pulling away from me. My FE then droped and I then slowed down and regained FE. As a rule of thumb maintaining 62-65 I recieve about 75 MPG when the instant FE display is half way in between 50 and 100 MPG. Even better FE can be acheived at 53-55 MPG, if you can maintain that speed on the highway. Also, recently I stoped using Cruise control which has increase my mileage on the drive to work due to the hills. This tank should be my best yet with between 53-55 Mpg with about 100 miles to go to finish out the tank. On flat ground the cruise is great and does not effect FE.