Today, once I passed the first 1000 km, I used for the first time the speed control and cruzed at 105 km/h. I was stunned to see the 5.8L/100 Km as average gas use. WOW ! I am sure that if I lower the speed, it would be better, but I don't want to. A 65 MPH speed is great for my commute (50 km round trip) of day to day.
In US metrics, that means 40.56 MPG at a 65 MPH speed !!
And yes, it all depends on how you drive.
My car setup : stock (no front tires inflate to 44 psi).
Temperature: 24 C degrees (shiny day)
Wind : 12 kmh