This is certainly unsubstantiated since there are many variables we didn't control, such as fuel quality, pavement, head wind, etc, but on a very extensive trip my family took last summer, our 2007 TCH always returned 42 MPG+ over 600 mile (or more) days, even in the Las Vegas heat. We noticed one day we were having trouble clearing 40 MPG and finally noticed the 'ECO' had been off. I'm sure it was cancelled in the morning for defrost and we forgot to turn it back on. We were down about 3 MPG (about 7% or so). I was surprised at the difference.

Not just Super White...Super Duper White...