I can't yet give a hard-and-fast rule on what mileage the car gets at X speed, but it definitely made only a small difference going 85 miles per hour instead of 80 miles per hour. There was a difference, perhaps around 2-3 mpg, it's hard to say. I spent most of the time going 80-82.

Mileage was never less than 20 mpg on the uphills and it was at 30 mpg on most of them, and of course at 50+ mpg on the downhills regardless of speed.

My mileage was slightly worse than the HCH on that segment, though it's possible it'll improve even more as the car breaks in... but possibly not. The HCH gets 40-42 mpg on the route, though it might have underestimated slightly. But its gas pedal was far more sensitive than the Camry's; if you press the Camry gas pedal more than you need to, the mileage lowers but your speed increases. So if your speed is constant, you know you're usually getting the best mileage you can, at least on the highway. With the HCH, on the other hand, often your foot might be too far down even though your speed isn't changing, and you can release the pressure to greatly increase mileage and your speed isn't affected, which was really annoying. So I had to often experiment with different foot pressures to find the one that got the best mileage while being just enough pressure to maintain speed.