Hills account for the difference, by the way. This car really makes you very sensitive to whether or not you're going uphill; surfaces I'd consider level I end up having to assist to go across one way, and the other way I get unusually high mileage. It's weird.

I never use cruise control so even I am interested in seeing what results NASA gets. Based on our earlier math, my guess is 39-40. But considering that's a 33% speed increase over 60 miles per hour, that's not that bad.

By the way, I have reason to suspect the trip meter is extremely inaccurate! For example, today, with 320 miles on Trip A, I coasted for a quarter of a mile and my trip MPG went from 36 to 43! So it's obviously wrong. And that's far from the first time I've seen that sort of thing -- it changes radically no matter how many miles I have on.

If you still think it's somehow possible for it to be accurate, let me show you in math. If I get 36 mpg over 320 miles then I used 8.89 gallons of gas over 320 miles. If I go a quarter of a mile using no gas then that's 320.25 miles divided by 8.89 = 36.02. So the computer's an idiot. And yes, that was a consistent 36 beforehand. Hell, even coasting 10 miles would give 37 mpg trip.

Maybe mine is broken (the gauge that measures precise fuel flow perhaps?) but it seems to underestimate more than anything else. 38 mpg on my first tank came as quite a shock since the computer for the longest time was suggesting I'd get like 33 mpg at best.