That was the point I was making. Hell, my current car averages 39 mpg and I drive it very gently and coast whenever I can, though I still get up to 80 mph on the highway. I drove a Prius around a bunch of highways at 80 mph with A/C off, using moderate or gentle acceleration, and got 46.5 mpg over 60-80 miles. Oh, both times the Prius was rented so the tires were probably at 32 PSI. Bringing them to 42 might have added 2 mpg.